KR102875182B1 - Electrolyte for lithium secondary battery and lithium secondary battery including thereof - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same, and provides a lithium secondary battery having an excellent lifespan even when subjected to high voltage, high rate, and high temperature by including a fluorinated anhydride (anhydride) as an additive.

Description

Electrolyte for lithium secondary battery and lithium secondary battery including the same {Electrolyte for lithium secondary battery and lithium secondary battery including its}

The present invention relates to a method for providing a lithium secondary battery having an excellent lifespan and improved safety even when high voltage and high rate are applied by including an electrolyte containing a fluorinated anhydride (anhydride).

Lithium secondary batteries have a mechanism where lithium ions, released from the positive electrode lithium metal oxide, migrate to the negative electrode carbon electrode and are intercalated into the carbon during initial charging. Due to lithium's strong reactivity, the surfaces of the negative electrode active material carbon particles and the positive electrode active material lithium metal oxide react with the electrolyte, forming a film called SEI (Solid Electrolyte Interphase) on the negative electrode surface.

This SEI is one of the key mechanisms of lithium secondary batteries that use electrolytes, and it plays a role in protecting the negative electrode while preventing further decomposition of the electrolyte.

In the case of the cathode, there are sufficient research cases on the above-mentioned SEI, but in the case of the anode, there are fewer research cases compared to the cathode SEI, but it is known that the existence of SEI in the anode can prevent the cathode material structure collapse phenomenon that occurs when metal is eluted due to the interface instability of the anode when a high voltage is applied.

However, as lithium secondary batteries become more high-performance, that is, as they are exposed to harsh usage environments that maintain high voltage, high rate (high current density for fast charging), and high temperatures, the problems of chemical structural instability and interface instability of positive and negative electrode materials become more serious, and even the risk of fire due to thermal runaway arises. Therefore, finding materials and technologies that improve stability and safety to solve these problems can be said to be a major challenge currently facing lithium secondary batteries.

Accordingly, the inventor of the present invention has invented an electrolyte capable of improving the high voltage, high rate, and high temperature characteristics of a lithium secondary battery while maintaining the general framework of the positive electrode, negative electrode, and non-aqueous organic electrolyte widely used in the art, and has thus provided an electrolyte capable of providing a lithium secondary battery with excellent life characteristics even when high voltage, high rate, and high temperature are applied.

(0001) Republic of Korea Patent Publication No. 10-2028647 (April 7, 2017) (0002) Republic of Korea Patent Publication No. 10-2020-0037612 (April 9, 2020) (0003) Japanese Patent Publication No. 2013-2114224 (October 10, 2013)

In order to solve the above problems, the present invention aims to provide an electrolyte containing a fluorinated anhydride (anhydride) and a lithium secondary battery containing the same.

One aspect of the present invention for achieving the above object relates to an electrolyte for a lithium secondary battery comprising a fluorinated anhydride (anhydride).

In the above aspect, the electrolyte for the lithium secondary battery may include a lithium salt and an organic solvent.

In the above aspect, the electrolyte for the lithium secondary battery may include a compound satisfying the following chemical formula 1.

[Chemical Formula 1]

(In the above chemical formula 1,

R ₁ and R ₂ are independently C1 to C4 alkyl or C1 to C4 fluorinated alkyl, wherein at least one of R ₁ and R ₂ contains fluorine.

In the above aspect, the organic solvent may include a compound satisfying the following chemical formula 2.

[Chemical Formula 2]

(In the above chemical formula 2,

R ₁ and R ₂ are independently CH ₃ or CH _x F _3-x (x is an integer from 0 to 3),

m and n are independent integers from 1 to 3.)

In the above aspect, the organic solvent may include a compound satisfying the following chemical formula 3.

[Chemical Formula 3]

(In the above chemical formula 3,

R ₁ and R ₂ are independently CH ₃ or CH _x F _3-x (x is an integer from 0 to 3),

m and n are independent integers from 1 to 3.)

In the above aspect, the organic solvent may include a compound satisfying the following chemical formula 4.

[Chemical Formula 4]

(In the above chemical formula 4,

X ₁ and X ₂ are independent of each other, H, F, CH ₃ or CH _x F _3-x (x is an integer from 0 to 2).

In the above aspect, the electrolyte for the lithium secondary battery may contain 0.01 to 5 parts by weight of a compound satisfying the chemical formula 1 based on 100 parts by weight of the mixture of the lithium salt and the organic solvent.

In the above aspect, the concentration of the lithium salt in the electrolyte for the lithium secondary battery may be 0.1 to 20 M.

In the above aspect, the electrolyte for the lithium secondary battery may be flame retardant or non-flammable with a self-extinguishing time (SET) of less than 20 sㆍg ^-1.

In addition, another aspect of the present invention relates to a lithium secondary battery including the electrolyte for the lithium secondary battery.

In another aspect of the above, the lithium secondary battery may include an electrolyte for a lithium secondary battery; a positive electrode; a negative electrode; and a separator.

In the case of an electrolyte for a lithium secondary battery containing a fluorinated anhydride (anhydride) according to the present invention, there is an improvement in that it has an excellent long-term lifespan even when high rates and high voltages are applied.

Figure 1 is a Nyquist plot showing the electrochemical impedance of Example 1 and Comparative Example 1.
Figure 2 is a Nyquist diagram showing the electrochemical impedance of Example 2 and Comparative Example 3.

Hereinafter, a lithium secondary battery electrolyte according to the present invention and a lithium secondary battery including the same will be described in detail. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Therefore, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be illustrated in an exaggerated manner to clarify the spirit of the present invention. At this time, unless otherwise defined, the technical and scientific terms used in the present invention have the meaning commonly understood by a person of ordinary skill in the art to which this invention pertains, and a description of well-known functions and configurations that may unnecessarily obscure the gist of the present invention in the following description and the accompanying drawings will be omitted.

The electrolyte for a lithium secondary battery provided in the present invention may include a compound satisfying the following chemical formula 1.

[Chemical Formula 1]

(In the above chemical formula 1,

R ₁ and R ₂ are independently C1 to C4 alkyl or C1 to C4 fluorinated alkyl, wherein at least one of R ₁ and R ₂ contains fluorine.

At this time, it is preferable that R ₁ and R ₂ are independent of each other C _n H _m F _(2n+1-m) (m and n are integers from 1 to 4 and m is integer from 0 to 9), and it is more preferable that n is 2 to 4 and m is 0.

Specifically, the compound satisfying the above chemical formula 1 is

Acetic fluoroacetic anhydride, acetic difluoroacetic anhydride, fluoroacetic anhydride, trifluoroacetic anhydride, acetic 2-fluoropropionic anhydride, acetic 3-fluoropropionic anhydride, acetic 2,2-difluoropropionic anhydride, acetic 2,3-difluoropropionic anhydride, acetic 3,3-difluoropropionic anhydride, acetic 2,2,3-trifluoropropionic anhydride, acetic 2,3,3-trifluoropropionic anhydride, acetic 3,3,3-trifluoropropionic anhydride, acetic 2,2,3,3-tetrafluoropropionic anhydride, acetic 2,3,3,3-tetrafluoropropionic anhydride, acetic pentafluoropropionic Anhydride, fluoroacetic 2-fluoropropionic anhydride, fluoroacetic 3-fluoropropionic anhydride, fluoroacetic 2,2-difluoropropionic anhydride, fluoroacetic 2,3-difluoropropionic anhydride, fluoroacetic 3,3-difluoropropionic anhydride, fluoroacetic 2,2,3-trifluoropropionic anhydride, fluoroacetic 2,3,3-trifluoropropionic anhydride, fluoroacetic 3,3,3-trifluoropropionic anhydride, fluoroacetic 2,2,3,3-tetrafluoropropionic anhydride, fluoroacetic 2,3,3,3-tetrafluoropropionic anhydride, fluoroacetic pentafluoropropionic anhydride, difluoroacetic 2-fluoropropionic anhydride, Difluoroacetic 3-fluoropropionic anhydride, difluoroacetic 2,2-difluoropropionic anhydride, difluoroacetic 2,3-difluoropropionic anhydride, difluoroacetic 3,3-difluoropropionic anhydride, difluoroacetic 2,2,3-trifluoropropionic anhydride, difluoroacetic 2,3,3-trifluoropropionic anhydride, difluoroacetic 3,3,3-trifluoropropionic anhydride, difluoroacetic 2,2,3,3-tetrafluoropropionic anhydride, difluoroacetic 2,3,3,3-tetrafluoropropionic anhydride, difluoroacetic pentafluoropropionic anhydride, trifluoroacetic 2-fluoropropionic anhydride, trifluoroacetic 3-fluoropropionic anhydride, trifluoroacetic 2,2-Difluoropropionic anhydride, trifluoroacetic 2,3-difluoropropionic anhydride, trifluoroacetic 3,3-difluoropropionic anhydride, trifluoroacetic 2,2,3-trifluoropropionic anhydride, trifluoroacetic 2,3,3-trifluoropropionic anhydride, trifluoroacetic 3,3,3-trifluoropropionic anhydride, trifluoroacetic 2,2,3,3-tetrafluoropropionic anhydride, trifluoroacetic 2,3,3,3-tetrafluoropropionic anhydride, trifluoroacetic pentafluoropropionic anhydride, propionic 2-fluoropropionic anhydride, propionic 3-fluoropropionic anhydride, propionic 2,2-difluoropropionic anhydride, propionic 2,3-Difluoropropionic anhydride, Propionic 3,3-difluoropropionic anhydride, Propionic 2,2,3-trifluoropropionic anhydride, Propionic 2,3,3-trifluoropropionic anhydride, Propionic 3,3,3-trifluoropropionic anhydride, Propionic 2,2,3,3-tetrafluoropropionic anhydride, Propionic 2,3,3,3-tetrafluoropropionic anhydride, Propionic pentafluoropropionic anhydride, 2-Fluoropropionic anhydride, 2-Fluoropropionic 3-fluoropropionic anhydride, 2-Fluoropropionic 2,2-difluoropropionic anhydride, 2-Fluoropropionic 2,3-difluoropropionic anhydride, 2-Fluoropropionic 3,3-Difluoropropionic anhydride, 2-Fluoropropionic 2,2,3-trifluoropropionic anhydride, 2-Fluoropropionic 2,3,3-trifluoropropionic anhydride, 2-Fluoropropionic 3,3,3-trifluoropropionic anhydride, 2-Fluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 2-Fluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 2-Fluoropropionic pentafluoropropionic anhydride, 3-Fluoropropionic 2-fluoropropionic anhydride, 3-Fluoropropionic anhydride, 3-Fluoropropionic 2,2-difluoropropionic anhydride, 3-Fluoropropionic 2,3-difluoropropionic anhydride, 3-Fluoropropionic 3,3-difluoropropionic anhydride, 3-Fluoropropionic 2,2,3-trifluoropropionic anhydride, 3-Fluoropropionic 2,3,3-trifluoropropionic anhydride, 3-Fluoropropionic 3,3,3-trifluoropropionic anhydride, 3-Fluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 3-Fluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 3-Fluoropropionic pentafluoropropionic anhydride, 2,2-difluoropropionic 2-fluoropropionic anhydride, 2,2-difluoropropionic 3-fluoropropionic anhydride, 2,2-difluoropropionic anhydride, 2,2-difluoropropionic 2,3-Difluoropropionic anhydride, 2,2-difluoropropionic 3,3-difluoropropionic anhydride, 2,2-difluoropropionic 2,2,3-trifluoropropionic anhydride, 2,2-difluoropropionic 2,3,3-trifluoropropionic anhydride, 2,2-difluoropropionic 3,3,3-trifluoropropionic anhydride, 2,2-difluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 2,2-difluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 2,2-difluoropropionic pentafluoropropionic anhydride, 2,3-difluoropropionic 2-fluoropropionic anhydride, 2,3-difluoropropionic 3-Fluoropropionic anhydride, 2,3-difluoropropionic 2,2-difluoropropionic anhydride, 2,3-difluoropropionic 2,3-difluoropropionic anhydride, 2,3-difluoropropionic 3,3-difluoropropionic anhydride, 2,3-difluoropropionic 2,2,3-trifluoropropionic anhydride, 2,3-difluoropropionic 2,3,3-trifluoropropionic anhydride, 2,3-difluoropropionic 3,3,3-trifluoropropionic anhydride, 2,3-difluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 2,3-difluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 2,3-difluoropropionic Pentafluoropropionic anhydride, 3,3-difluoropropionic 2-fluoropropionic anhydride, 3,3-difluoropropionic 3-fluoropropionic anhydride, 3,3-difluoropropionic 2,2-difluoropropionic anhydride, 3,3-difluoropropionic 2,3-difluoropropionic anhydride, 3,3-difluoropropionic 3,3-difluoropropionic anhydride, 3,3-difluoropropionic 2,2,3-trifluoropropionic anhydride, 3,3-difluoropropionic 2,3,3-trifluoropropionic anhydride, 3,3-difluoropropionic 3,3,3-trifluoropropionic anhydride, 3,3-difluoropropionic 2,2,3,3-tetrafluoropropionic Anhydride, 3,3-difluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 3,3-difluoropropionic pentafluoropropionic anhydride, 2,2,3-trifluoropropionic 2-fluoropropionic anhydride, 2,2,3-trifluoropropionic 3-fluoropropionic anhydride, 2,2,3-trifluoropropionic 2,2-difluoropropionic anhydride, 2,2,3-trifluoropropionic 2,3-difluoropropionic anhydride, 2,2,3-trifluoropropionic 3,3-difluoropropionic anhydride, 2,2,3-trifluoropropionic 2,2,3-trifluoropropionic anhydride, 2,2,3-trifluoropropionic 2,3,3-trifluoropropionic Anhydride, 2,2,3-trifluoropropionic 3,3,3-trifluoropropionic anhydride, 2,2,3-trifluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 2,2,3-trifluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 2,2,3-trifluoropropionic pentafluoropropionic anhydride, 2,3,3-trifluoropropionic 2-fluoropropionic anhydride, 2,3,3-trifluoropropionic 3-fluoropropionic anhydride, 2,3,3-trifluoropropionic 2,2-difluoropropionic anhydride, 2,3,3-trifluoropropionic 2,3-difluoropropionic anhydride, 2,3,3-trifluoropropionic 3,3-Difluoropropionic anhydride, 2,3,3-trifluoropropionic 2,2,3-trifluoropropionic anhydride, 2,3,3-trifluoropropionic 2,3,3-trifluoropropionic anhydride, 2,3,3-trifluoropropionic 3,3,3-trifluoropropionic anhydride, 2,3,3-trifluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 2,3,3-trifluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 2,3,3-trifluoropropionic pentafluoropropionic anhydride, 3,3,3-trifluoropropionic 2-fluoropropionic anhydride, 3,3,3-trifluoropropionic 3-fluoropropionic anhydride, 3,3,3-Trifluoropropionic 2,2-difluoropropionic anhydride, 3,3,3-Trifluoropropionic 2,3-difluoropropionic anhydride, 3,3,3-Trifluoropropionic 3,3-difluoropropionic anhydride, 3,3,3-Trifluoropropionic 2,2,3-trifluoropropionic anhydride, 3,3,3-Trifluoropropionic 2,3,3-trifluoropropionic anhydride, 3,3,3-Trifluoropropionic 3,3,3-trifluoropropionic anhydride, 3,3,3-Trifluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 3,3,3-Trifluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 3,3,3-Trifluoropropionic pentafluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2-fluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 3-fluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2,2-difluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2,3-difluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 3,3-difluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2,2,3-trifluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2,3,3-trifluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 3,3,3-trifluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, 2,2,3,3-Tetrafluoropropionic pentafluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2-fluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 3-fluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2,2-difluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2,3-difluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 3,3-difluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2,2,3-trifluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2,3,3-trifluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 3,3,3-trifluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2,2,3,3-Tetrafluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic 2,3,3,3-Tetrafluoropropionic anhydride, 2,3,3,3-Tetrafluoropropionic pentafluoropropionic anhydride, pentafluoropropionic 2-Fluoropropionic anhydride, pentafluoropropionic It may be selected from the group consisting of 3-fluoropropionic anhydride, pentafluoropropionic 2,2-difluoropropionic anhydride, pentafluoropropionic 2,3-difluoropropionic anhydride, pentafluoropropionic 3,3-difluoropropionic anhydride, pentafluoropropionic 2,2,3-trifluoropropionic anhydride, pentafluoropropionic 2,3,3-trifluoropropionic anhydride, pentafluoropropionic 3,3,3-trifluoropropionic anhydride, pentafluoropropionic 2,2,3,3-tetrafluoropropionic anhydride, pentafluoropropionic 2,3,3,3-tetrafluoropropionic anhydride, and pentafluoropropionic anhydride.

The electrolyte for a lithium secondary battery provided in the present invention may include a lithium salt and an organic solvent.

The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO 4, LiAlCl ₄ , LiCF ₃ SO ₃ , LiC _{4 F 9 SO 3} , LiC ₆ H ₅ 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 any one or a mixture of two or more selected from the group consisting of LiN(FSO ₂ ) ₂ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+ 1 SO ₂ ) (wherein x and y are 0 or natural numbers), LiCl, _LiI , LiSCN, LiB(C _{2 O 4} ) ₂ , LiF ₂ BC _{2 O 4 ,} LiPF ₄ (C ₂ O ₄ ), LiPF 2 (C ₂ O ₄ ) ₂ , and LiP(C 2 O 4 ) ₃ , and this is just one example, and any one commonly used in the art may be used without particular limitation, and is not necessarily limited thereto.

The above organic solvent may include a compound satisfying the following chemical formula 2.

[Chemical Formula 2]

(In the above chemical formula 2,

R ₁ and R ₂ are independently CH ₃ or CH _x F _3-x (x is an integer from 0 to 3),

m and n are independent integers from 0 to 3.)

For example, compounds satisfying the above chemical formula 2 include linear carbonate-based substances and linear fluorinated carbonate-based substances, such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 2-fluoromethyl methyl carbonate, and 2-fluoroethyl methyl carbonate, methyl (2,2,2-trifluoroethyl) carbonate, and di-2,2,2-trifluoroethyl carbonate.

The above organic solvent may include a compound satisfying the following chemical formula 3.

[Chemical Formula 3]

(In the above chemical formula 3,

R ₁ and R ₂ are independently CH ₃ or CH _x F _3-x (x is an integer from 0 to 3),

m and n are independent integers from 0 to 3.)

For example, compounds satisfying the above chemical formula 3 include linear esters and linear fluorinated esters such as methyl acetate, methyl propionate, ethyl acetate, 2,2,2-trifluoroethyl acetate, 2,2-difluoroethyl acetate, 2-fluoroethyl acetate, trifluoromethyl acetate, difluoromethyl acetate, fluoro methyl acetate, and 2,2,2-trifluoroethyl propionate.

The above organic solvent may include a compound satisfying the following chemical formula 4.

[Chemical Formula 4]

(In the above chemical formula 4,

X ₁ and X ₂ are independent of each other, H, F, CH ₃ or CH _x F _3-x (x is an integer from 0 to 2).

For example, compounds satisfying the above chemical formula 4 include cyclic carbonate substances such as ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and 4,4-difluoroethylene carbonate, and fluorinated cyclic carbonate substances.

The above electrolyte for a lithium secondary battery may further include an organic solvent other than the compounds satisfying the above chemical formulas 2 to 4. Specifically, dimethyl ether, ethyl methyl ether, diethyl ether, propyl methyl ether, propyl ethyl ether, dipropyl ether, isopropyl methyl ether, isopropyl ethyl ether, diisopropyl ether, n-butyl methyl ether, n-butyl ethyl ether, n-butylpropyl ether, n-butylisopropyl ether, n-dibutyl ether, tert-butyl methyl ether, tert-butyl ethyl ether, tert-butylpropyl ether, tert-butylisopropyl ether, tert-dibutyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol isopropyl ether, ethylene glycol n-butyl ether, ethylene glycol tert-butyl ether, diethylene glycol ether, propylene glycol methyl A group consisting of ethers such as ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol isopropyl ether, propylene glycol n-butyl ether, propylene glycol tert-butyl ether, and dipropylene glycol ether; Fluoromethyl methyl ether, difluoromethyl methyl ether, trifluoromethyl methyl ether, di(fluoromethyl) ether, difluoromethyl fluoromethyl ether, trifluoromethyl fluoromethyl ether, di(difluoromethyl) ether, trifluoromethyl difluoromethyl ether, di(trifluoromethyl) ether, 1-fluoroethyl methyl ether, 2-fluoroethyl methyl ether, 1,1-difluoroethyl methyl ether, 1,2-difluoroethyl methyl ether, 2,2-difluoroethyl methyl ether, 1,1,1-trifluoroethyl methyl ether, 1,1,2-trifluoroethyl methyl ether, 1,2,2-trifluoroethyl methyl ether, 2,2,2-trifluoroethyl methyl ether, 1,1,1,2-tetrafluoroethyl methyl ether, 1,1,2,2-Tetrafluoroethyl methyl ether, 1,2,2,2-Tetrafluoroethyl methyl ether, Pentafluoroethyl methyl ether, 1,1,2,2,2-Pentafluoroethyl methyl ether, Hexafluoroethyl methyl ether, 1-Fluoroethyl fluoromethyl ether, 2-Fluoroethyl fluoromethyl ether, 1,1-Difluoroethyl fluoromethyl ether, 1,2-Difluoroethyl fluoromethyl ether, 2,2-Difluoroethyl fluoromethyl ether, 1,1,1-Trifluoroethyl fluoromethyl ether, 1,1,2-Trifluoroethyl fluoromethyl ether, 1,2,2-Trifluoroethyl fluoromethyl ether, 2,2,2-Trifluoroethyl fluoromethyl ether, 1,1,1,2-Tetrafluoroethyl fluoromethyl ether, 1,1,2,2-Tetrafluoroethyl Fluoromethyl ether, 1,2,2,2-tetrafluoroethyl fluoromethyl ether, pentafluoroethyl fluoromethyl ether, 1,1,2,2,2-pentafluoroethyl fluoromethyl ether, hexafluoroethyl fluoromethyl ether, 1-fluoroethyl difluoromethyl ether, 2-fluoroethyl difluoromethyl ether, 1,1-difluoroethyl difluoromethyl ether, 1,2-difluoroethyl difluoromethyl ether, 2,2-difluoroethyl difluoromethyl ether, 1,1,1-trifluoroethyl difluoromethyl ether, 1,1,2-trifluoroethyl difluoromethyl ether, 1,2,2-trifluoroethyl difluoromethyl ether, 2,2,2-trifluoroethyl difluoromethyl ether, 1,1,1,2-tetrafluoroethyl difluoromethyl ether, 1,1,2,2-tetrafluoroethyl difluoromethyl ether, 1,2,2,2-Tetrafluoroethyl difluoromethyl ether, pentafluoroethyl difluoromethyl ether, 1,1,2,2,2-pentafluoroethyl difluoromethyl ether, hexafluoroethyl difluoromethyl ether, 1-fluoroethyl trifluoromethyl ether, 2-fluoroethyl trifluoromethyl ether, 1,1-difluoroethyl trifluoromethyl ether, 1,2-difluoroethyl trifluoromethyl ether, 2,2-difluoroethyl trifluoromethyl ether, 1,1,1-trifluoroethyl trifluoromethyl ether, 1,1,2-trifluoroethyl trifluoromethyl ether, 1,2,2-trifluoroethyl trifluoromethyl ether, 2,2,2-trifluoroethyl trifluoromethyl ether, 1,1,1,2-tetrafluoroethyl trifluoromethyl ether, 1,1,2,2-tetrafluoroethyl trifluoromethyl ether, 1,2,2,2-Tetrafluoroethyl trifluoromethyl ether, pentafluoroethyl trifluoromethyl ether, 1,1,2,2,2-pentafluoroethyl trifluoromethyl ether, hexafluoroethyl trifluoromethyl ether, 1-Fluoroethyl ethyl ether, 2-Fluoroethyl ethyl ether, 1,1-Difluoroethyl ethyl ether, 1,2-Difluoroethyl ethyl ether, 2,2-Difluoroethyl ethyl ether, 1,1,1-Trifluoroethyl ethyl ether, 1,1,2-Trifluoroethyl ethyl ether, 1,2,2-Trifluoroethyl ethyl ether, 2,2,2-Trifluoroethyl ethyl ether, 1,1,1,2-Tetrafluoroethyl ethyl ether, 1,1,2,2-Tetrafluoroethyl ethyl ether, 1,2,2,2-Tetrafluoroethyl ethyl ether, Pentafluoroethyl ethyl ether, 1,1,2,2,2-pentafluoroethyl ethyl ether, hexafluoroethyl ethyl ether, 1-fluoroethyl 1-fluoroethyl ether, 2-fluoroethyl 1-fluoroethyl ether, 1,1-difluoroethyl 1-fluoroethyl ether, 1,2-difluoroethyl 1-fluoroethyl ether, 2,2-difluoroethyl 1-fluoroethyl ether, 1,1,1-trifluoroethyl 1-fluoroethyl ether, 1,1,2-trifluoroethyl 1-fluoroethyl ether, 1,2,2-trifluoroethyl 1-fluoroethyl ether, 2,2,2-trifluoroethyl 1-fluoroethyl ether, 1,1,1,2-tetrafluoroethyl 1-fluoroethyl ether, 1,1,2,2-tetrafluoroethyl 1-fluoroethyl ether, 1,2,2,2-Tetrafluoroethyl 1-fluoroethyl ether, pentafluoroethyl 1-fluoroethyl ether, 1,1,2,2,2-pentafluoroethyl 1-fluoroethyl ether, hexafluoroethyl 1-fluoroethyl ether, 1-fluoroethyl 2-fluoroethyl ether, 2-fluoroethyl 2-fluoroethyl ether, 1,1-difluoroethyl 2-fluoroethyl ether, 1,2-difluoroethyl 2-fluoroethyl ether, 2,2-difluoroethyl 2-fluoroethyl ether, 1,1,1-trifluoroethyl 2-fluoroethyl ether, 1,1,2-trifluoroethyl 2-fluoroethyl ether, 1,2,2-trifluoroethyl 2-fluoroethyl ether, 2,2,2-trifluoroethyl 2-fluoroethyl ether, 1,1,1,2-tetrafluoroethyl 2-fluoroethyl Ether, 1,1,2,2-tetrafluoroethyl 2-fluoroethyl ether, 1,2,2,2-tetrafluoroethyl 2-fluoroethyl ether, pentafluoroethyl 2-fluoroethyl ether, pentafluoroethyl 2-fluoroethyl ether, hexafluoroethyl 2-fluoroethyl ether, 1-fluoroethyl 1,2-difluoroethyl ether, 2-fluoroethyl 1,2-difluoroethyl ether, 1,1-difluoroethyl 1,2-difluoroethyl ether, di(1,2-difluoroethyl) ether, 2,2-difluoroethyl 1,2-difluoroethyl ether, 1,1,1-trifluoroethyl 1,2-difluoroethyl ether, 1,1,2-trifluoroethyl 1,2-difluoroethyl ether, 1,2,2-trifluoroethyl 1,2-difluoroethyl ether, 2,2,2-Trifluoroethyl 1,2-difluoroethyl ether, 1,1,1,2-tetrafluoroethyl 1,2-difluoroethyl ether, 1,1,2,2-tetrafluoroethyl 1,2-difluoroethyl ether, 1,2,2,2-tetrafluoroethyl 1,2-difluoroethyl ether, pentafluoroethyl 1,2-difluoroethyl ether, pentafluoroethyl 1,2-difluoroethyl ether, hexafluoroethyl 1,2-difluoroethyl ether, 1,1-difluoroethyl 2,2-difluoroethyl ether, 1,2-difluoroethyl 2,2-difluoroethyl ether, di(2,2-difluoroethyl) ether, 1,1,1-trifluoroethyl 2,2-difluoroethyl ether, 1,1,2-trifluoroethyl 2,2-difluoroethyl ether, 1,2,2-Trifluoroethyl 2,2-difluoroethyl ether, 2,2,2-Trifluoroethyl 2,2-difluoroethyl ether, 1,1,1,2-Tetrafluoroethyl 2,2-difluoroethyl ether, 1,1,2,2-Tetrafluoroethyl 2,2-difluoroethyl ether, 1,2,2,2-Tetrafluoroethyl 2,2-difluoroethyl ether, Pentafluoroethyl 2,2-difluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 2,2-difluoroethyl ether, Hexafluoroethyl 2,2-difluoroethyl ether, 1,1-Difluoroethyl 1,1,1-Trifluoroethyl ether, 1,2-Difluoroethyl 1,1,1-Trifluoroethyl ether, 2,2-Difluoroethyl 1,1,1-Trifluoroethyl Ether, di(1,1,1-trifluoroethyl) ether, 1,1,2-trifluoroethyl 1,1,1-trifluoroethyl ether, 1,2,2-trifluoroethyl 1,1,1-trifluoroethyl ether, 2,2,2-trifluoroethyl 1,1,1-trifluoroethyl ether, 1,1,1,2-tetrafluoroethyl 1,1,1-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl 1,1,1-trifluoroethyl ether, 1,2,2,2-tetrafluoroethyl 1,1,1-trifluoroethyl ether, pentafluoroethyl 1,1,1-trifluoroethyl ether, 1,1,2,2,2-pentafluoroethyl 1,1,1-trifluoroethyl ether, hexafluoroethyl 1,1,1-Trifluoroethyl ether, 1,1-difluoroethyl 1,1,2-trifluoroethyl ether, 1,2-difluoroethyl 1,1,2-trifluoroethyl ether, 2,2-difluoroethyl 1,1,2-trifluoroethyl ether, 1,1,1-trifluoroethyl 1,1,2-trifluoroethyl ether, 1,1,2-trifluoroethyl 1,1,2-trifluoroethyl ether, 1,2,2-trifluoroethyl 1,1,2-trifluoroethyl ether, 2,2,2-trifluoroethyl 1,1,2-trifluoroethyl ether, 1,1,1,2-tetrafluoroethyl 1,1,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl 1,1,2-trifluoroethyl ether, 1,2,2,2-tetrafluoroethyl 1,1,2-Trifluoroethyl ether, pentafluoroethyl 1,1,2-Trifluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 1,1,2-Trifluoroethyl ether, hexafluoroethyl 1,1,2-Trifluoroethyl ether, 1,1-Difluoroethyl 1,2,2-Trifluoroethyl ether, 1,2-Difluoroethyl 1,2,2-Trifluoroethyl ether, 2,2-Difluoroethyl 1,2,2-Trifluoroethyl ether, 1,1,1-Trifluoroethyl 1,2,2-Trifluoroethyl ether, 1,1,2-Trifluoroethyl 1,2,2-Trifluoroethyl ether, Di(1,2,2-Trifluoroethyl) ether, 2,2,2-Trifluoroethyl 1,2,2-Trifluoroethyl ether, 1,1,1,2-Tetrafluoroethyl 1,2,2-Trifluoroethyl ether, 1,1,2,2-Tetrafluoroethyl 1,2,2-Trifluoroethyl ether, 1,2,2,2-Tetrafluoroethyl 1,2,2-Trifluoroethyl ether, Pentafluoroethyl 1,2,2-Trifluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 1,2,2-Trifluoroethyl ether, Hexafluoroethyl 1,2,2-Trifluoroethyl ether, 1,1-Difluoroethyl 2,2,2-Trifluoroethyl ether, 1,2-Difluoroethyl 2,2,2-Trifluoroethyl ether, 2,2-Difluoroethyl 2,2,2-Trifluoroethyl ether, 1,1,1-Trifluoroethyl 2,2,2-Trifluoroethyl ether, 1,2,2-Trifluoroethyl 2,2,2-Trifluoroethyl ether, di(2,2,2-trifluoroethyl) ether, 1,1,1,2-Tetrafluoroethyl 2,2,2-Trifluoroethyl ether, 1,1,2,2-Tetrafluoroethyl 2,2,2-Trifluoroethyl ether, 1,2,2,2-Tetrafluoroethyl 2,2,2-Trifluoroethyl ether, pentafluoroethyl 2,2,2-Trifluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 2,2,2-Trifluoroethyl ether, Hexafluoroethyl 2,2,2-Trifluoroethyl ether, 1,1-Difluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 1,2-Difluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 2,2-Difluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 1,1,1-Trifluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 1,1,2-Trifluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 1,2,2-Trifluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 2,2,2-Trifluoroethyl 1,1,1,2-Tetrafluoroethyl ether, Di(1,1,1,2-Tetrafluoroethyl) ether, 1,1,2,2-Tetrafluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 1,2,2,2-Tetrafluoroethyl 1,1,1,2-Tetrafluoroethyl ether, Pentafluoroethyl 1,1,1,2-Tetrafluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 1,1,1,2-Tetrafluoroethyl ether, Hexafluoroethyl 1,1,1,2-tetrafluoroethyl ether, 1,1-difluoroethyl 1,1,2,2-tetrafluoroethyl ether, 1,2-difluoroethyl 1,1,2,2-tetrafluoroethyl ether, 2,2-difluoroethyl 1,1,2,2-tetrafluoroethyl ether, 1,1,1-trifluoroethyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2-trifluoroethyl 1,1,2,2-tetrafluoroethyl ether, 1,2,2-trifluoroethyl 1,1,2,2-tetrafluoroethyl ether, 2,2,2-trifluoroethyl 1,1,2,2-tetrafluoroethyl ether, 1,1,1,2-tetrafluoroethyl 1,1,2,2-tetrafluoroethyl ether, di(1,1,2,2-tetrafluoroethyl) ether, 1,2,2,2-Tetrafluoroethyl 1,1,2,2-Tetrafluoroethyl ether, pentafluoroethyl 1,1,2,2-Tetrafluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 1,1,2,2-Tetrafluoroethyl ether, Hexafluoroethyl 1,1,2,2-Tetrafluoroethyl ether, 1,1-Difluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,2-Difluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 2,2-Difluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,1,1-Trifluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,1,2-Trifluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,2,2-Trifluoroethyl 1,2,2,2-Tetrafluoroethyl Ether, 2,2,2-Trifluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,1,1,2-Tetrafluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,1,2,2-Tetrafluoroethyl 1,2,2,2-Tetrafluoroethyl ether, Di(1,2,2,2-Tetrafluoroethyl) ether, Pentafluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,1,2,2,2-Pentafluoroethyl 1,2,2,2-Tetrafluoroethyl ether, Hexafluoroethyl 1,2,2,2-Tetrafluoroethyl ether, 1,1-Difluoroethyl Pentafluoroethyl Ether, 1,2-Difluoroethyl Pentafluoroethyl Ether, 2,2-Difluoroethyl Pentafluoroethyl Ether, 1,1,1-Trifluoroethyl Pentafluoroethyl Ether, 1,1,2-Trifluoroethyl pentafluoroethyl ether, 1,2,2-Trifluoroethyl pentafluoroethyl ether, 2,2,2-Trifluoroethyl pentafluoroethyl ether, 1,1,1,2-Tetrafluoroethyl pentafluoroethyl ether, 1,1,2,2-Tetrafluoroethyl pentafluoroethyl ether, 1,2,2,2-Tetrafluoroethyl pentafluoroethyl ether, Di(pentafluoroethyl) ether, 1,1,2,2,2-Pentafluoroethyl pentafluoroethyl ether, Hexafluoroethyl pentafluoroethyl ether, 1,1-Difluoroethyl 1,1,2,2,2-Pentafluoroethyl ether, 1,2-Difluoroethyl 1,1,2,2,2-Pentafluoroethyl ether, 2,2-Difluoroethyl 1,1,2,2,2-Pentafluoroethyl ether, 1,1,1-Trifluoroethyl 1,1,2,2,2-pentafluoroethyl ether, 1,1,2-Trifluoroethyl 1,1,2,2,2-pentafluoroethyl ether, 1,2,2-Trifluoroethyl 1,1,2,2,2-pentafluoroethyl ether, 2,2,2-Trifluoroethyl 1,1,2,2,2-pentafluoroethyl ether, 1,1,1,2-Tetrafluoroethyl 1,1,2,2,2-pentafluoroethyl ether, 1,1,2,2,2-Tetrafluoroethyl 1,1,2,2,2-pentafluoroethyl ether, 1,2,2,2-Tetrafluoroethyl 1,1,2,2,2-pentafluoroethyl ether, Pentafluoroethyl 1,1,2,2,2-pentafluoroethyl ether, A group consisting of fluorinated ethers such as di(1,1,2,2,2-pentafluoroethyl) ether, hexafluoroethyl pentafluoroethyl ether, and dihexafluoroethyl ether; and bis(fluoromethyl)sulfate, bis(2-fluoroethyl)sulfate, bis(3-fluoropropyl)sulfate, bis(difluoromethyl)sulfate, bis(2,2-difluoroethyl)sulfate, bis(3,3-difluoropropyl)sulfate, bis(trifluoromethyl)sulfate, bis(2,2,2-trifluoroethyl)sulfate, bis(3,3,3-trifluoropropyl)sulfate, methyl(fluoromethyl)sulfate, methyl(2-fluoroethyl)sulfate, methyl(3-fluoropropyl)sulfate, methyl(difluoromethyl)sulfate, methyl(2,2-difluoroethyl)sulfate, methyl(3,3-difluoropropyl)sulfate, methyl(trifluoromethyl)sulfate, methyl(2,2,2-trifluoroethyl)sulfate, methyl(3,3,3-trifluoropropyl)sulfate, Ethyl (fluoromethyl) sulfate, ethyl (2-fluoroethyl) sulfate, ethyl (3-fluoropropyl) sulfate, ethyl (difluoromethyl) sulfate, ethyl (2,2-difluoroethyl) sulfate, ethyl (3,3-difluoropropyl) sulfate, ethyl (trifluoromethyl) sulfate, ethyl (2,2,2-trifluoroethyl) sulfate, ethyl (3,3,3-trifluoropropyl) sulfate, propyl (fluoromethyl) sulfate, propyl (2-fluoroethyl) sulfate, propyl (3-fluoropropyl) sulfate, propyl (difluoromethyl) sulfate, propyl (2,2-difluoroethyl) sulfate, propyl (3,3,3-trifluoropropyl) sulfate, propyl (trifluoromethyl) sulfate, propyl (2,2,2-trifluoroethyl) sulfate, propyl (3,3,3-trifluoropropyl) sulfate, (fluoromethyl) (2-fluoroethyl) sulfate, (Fluoromethyl)(3-fluoropropyl)sulfate, (Fluoromethyl)(difluoromethyl)sulfate, (Fluoromethyl)(2,2-difluoroethyl)sulfate, (Fluoromethyl)(3,3-difluoropropyl)sulfate, (Fluoromethyl)(trifluoromethyl)sulfate, (Fluoromethyl)(2,2,2-trifluoroethyl)sulfate, (Fluoromethyl)(3,3,3-trifluoropropyl)sulfate, (2-Fluoroethyl)(3-fluoropropyl)sulfate, (2-Fluoroethyl)(difluoromethyl)sulfate, (2-Fluoroethyl)(2,2-difluoroethyl)sulfate, (2-Fluoroethyl)(3,3-difluoropropyl)sulfate, (2-Fluoroethyl)(trifluoromethyl)sulfate, (2-Fluoroethyl)(2,2,2-trifluoroethyl)sulfate, (2-Fluoroethyl)(3,3,3-trifluoropropyl)sulfate, (3-Fluoropropyl)(difluoromethyl)sulfate, (3-Fluoropropyl)(2,2-difluoroethyl)sulfate, (3-Fluoropropyl)(3,3-difluoropropyl)sulfate, (3-Fluoropropyl)(trifluoromethyl)sulfate, (3-Fluoropropyl)(2,2,2-trifluoroethyl)sulfate, (3-Fluoropropyl)(3,3,3-trifluoropropyl)sulfate, (difluoromethyl)(2,2-difluoroethyl)sulfate, (difluoromethyl)(3,3-difluoropropyl)sulfate, (difluoromethyl)(trifluoromethyl)sulfate, (difluoromethyl)(2,2,2-trifluoroethyl)sulfate, (difluoromethyl)(3,3,3-trifluoropropyl)sulfate, (2,2-difluoroethyl)(3,3-difluoropropyl)sulfate, (2,2-difluoroethyl)(trifluoromethyl)sulfate, The organic solvent may be at least one selected from the group consisting of sulfate-based solvents such as (2,2-difluoroethyl)(2,2,2-trifluoroethyl)sulfate, (2,2-difluoroethyl)(3,3,3-trifluoropropyl)sulfate, (3,3-difluoropropyl)trifluoromethyl)sulfate, (3,3-difluoropropyl)(2,2,2-trifluoroethyl)sulfate and (3,3-difluoropropyl)(3,3,3-trifluoropropyl)sulfate; However, this is only an example and any solvent commonly used in the art can be used without particular limitation and is not necessarily limited thereto. Preferably, the organic solvent may be a mixture of any two or more selected from the above-mentioned cyclic carbonate-based solvents, fluorinated cyclic carbonate-based solvents, linear carbonate-based solvents, fluorinated linear carbonate-based solvents, linear ester-based solvents and fluorinated ester-based solvents.

At this time, the electrolyte for the lithium secondary battery may contain 0.01 to 5 parts by weight of a compound satisfying the chemical formula 1, with respect to 100 parts by weight of the mixture of the lithium salt and the organic solvent, preferably 0.1 to 3 parts by weight, and more preferably 0.2 to 1 part by weight.

The concentration of the electrolyte for the lithium secondary battery can be adjusted to a level commonly used in the art, and specifically, for example, the concentration of the lithium salt in the electrolyte can be 0.1 to 20 M, preferably 0.2 to 10 M, and more preferably 0.5 to 1.5 M.

The above electrolyte for a lithium secondary battery may further contain an additive.

The above additive may be an additive that directly forms or assists in the formation of a solid-electrolyte interphase (SEI) of the negative electrode and the positive electrode; an additive that increases the ionic conductivity of the SEI; an additive that removes active materials such as HF and PF ₅ ; an additive that prevents overcharge; an additive that increases flame retardancy; an additive that promotes uniform reduction deposition of lithium; an additive that assists in the solvation phenomenon of ions; or an additive that prevents corrosion of the current collector.

Additives that assist in the formation of the SEI of the above anode include, for example, a group consisting of boron series such as trimethyl boroxine (TMB), triethyl boroxine, trimethyl borate, triethyl borate (TEB), and tris(trimethylsilyl) borate (TMSB); a group consisting of sulfur series such as 4,4-bi(1,3,2-dioxathiolane)2,2-dioxide (BDTD), 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphospholane-2-oxide (TFEOP); And the group consisting of fluorinated compounds added in combination with fluoroethylene carbonate (FEC), such as methyl 2,2,2-trifluoroethyl carbonate (FEMC), methyl difluroacetate (DFMAc), and ethyl difluoroacetate (DFEAc); the group consisting of phosphate and fluorinated phosphate compounds; the group consisting of phosphonate compounds; etc., may be at least one selected from the group consisting of additives that assist in the formation of SEI of a known positive electrode, and are not necessarily limited to the above examples.

Additives that directly form or assist in the formation of the SEI of the above-mentioned negative electrode include, for example, cyclic compounds such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), allyl ethyl carbonate, vinyl acetate, divinyl adipate, acrylic acid nitrile, 2-vinyl pyridine, γ-butyrolactone (GBL), methyl phenyl carbonate, succinic imide, maleic acid anhydride, succinic acid anhydride, methyl chloroformate, methyl cinnamate, and furan derivatives having double bonds. A group consisting of compounds; a group consisting of phosphate and fluorinated phosphate compounds; a group consisting of phosphonate compounds; a group consisting of vinyl-containing silane compounds; and a group consisting of nitrate and nitrite compounds; may be any one or more selected from the group consisting of compounds, but any additive that directly forms or assists in the formation of a known SEI may be used, and is not necessarily limited to the above examples.

Additives that increase the ionic conductivity of the above SEI include, for example, LiPO ₃ F ₂ , 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 any one or a mixture of two or more selected from the group consisting of LiN(FSO ₂ ) ₂ , LiN(C _x F _{2x+ 1} SO ₂ )(C _{y F} 2y+1 SO ₂ ) _{(wherein x and y are 0 or natural numbers), LiB(C 2 O 4 ) 2 , LiF 2 B(C 2 O 4 ) , LiF 2 B ( FC 3 O 4 ) ,} LiPF 4 (C ₂ O ₄ ), LiPF 2 (C 2 O 4 ) 2 , LiP(C 2 O 4 ) ₃ , sulfone-based, sultone-based, sulfite-based, and sulfate-based, but is not necessarily limited thereto.

Additives that remove the above active substance include, for example, a group having an isocyanate (N=C=O) functional group such as p-toluene sulfonyl isocyanate (PTSI); a group of pyrrolidinones such as 1-methyl-2-pyrrolidinone; a group of silane derivatives having a Si-O structure such as dimethoxy dimethyl silane (DODSi) and diphenyl dimethoxy silane (DPDMS); a group of phosphoramides such as hexamethyl phosphoramide; The additive may be at least one selected from the group consisting of phosphites such as tris(2,2,2-trifluoroethyl)phosphite, tris(trimethyl silyl)phosphite (TMSPi), etc.; and phosphonites such as diethyl phenyl phosphonite (DEPP), etc.; but any additive that removes a known active substance may be used, and is not necessarily limited to the above examples.

The additive for preventing overcharge may be at least one selected from the group consisting of organic compounds such as metallocenes, tetracyano ethylene, tetramethyl phenylene diamine, dihydrophenazine, bipyridyl carbonates, biphenyl carbonates, 2,7-diacetyl thianthrene, and phenothiazine; and the group consisting of lithium salts such as Li ₂ B ₁₂ F _x H _12-x (lithium fluorododecaborates), lithium bis(oxalato)borate (LiBOB); However, any known additive for preventing overcharge may be used, and is not necessarily limited to the above examples.

The additive that increases the flame retardancy may be at least one selected from, for example, a group consisting of alkyl phosphates such as trimethyl phosphate and triethyl phosphate; a group consisting of fluorinated phosphates such as tris(2,2,2-trifluoroethyl)phosphate; a group consisting of phosphazenes such as hexamethoxy cyclophosphazene; a group consisting of fluorinated ethers and fluorinated carbonates such as methyl nonafluorobutyl ether (MFE), fluoroethylene carbonate, and fluoropropylene carbonate; etc., but any additive that is known to increase the flame retardancy may be used, and is not necessarily limited to the above examples.

The additive that promotes the uniform reduction deposition of lithium may be, for example, at least one selected from lithium nitride (LiNO ₃ ), tetrahydrofuran, 2-methyltetrahydrofuran, thiophene, 2-methylthiophene, nitromethane, tetraalkylammonium chloride, cetyl trimethyl ammonium chloride, lithium perfluorooctane sulfonate, tetraethylammonium perfluorooctane sulfonate, perfluoropolyethers, AlI ₃ , and SnI ₂ , but any additive that promotes the uniform reduction deposition of lithium known in the art may be used, and is not necessarily limited to the above examples.

The additive that helps the solvation phenomenon of the above ion may be, for example, one or more selected from 12-crown-4 and its derivatives, tris(pentafluorophenyl)borane, cyclic aza-ether compounds, and borole compounds, but any additive that helps the solvation phenomenon of a known ion may be used, and is not necessarily limited to the above examples.

The additive for preventing corrosion of the above-mentioned collector may include, for example, a lithium salt compound having a chemical formula of LiPF ₆ , LiBF ₄ , LiN(SO ₂ C _n F _2n+1 ) ₂ (n=2 to 4).

The content of the above additive can be adjusted in the range of 0.01 to 10 wt% based on the weight of the electrolyte for a lithium secondary battery depending on the desired properties.

The self-extinguishing time (SET) of the electrolyte for the above lithium secondary battery may be less than 20 sㆍg ^-1 .

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

The above lithium secondary battery may include an electrolyte for a lithium secondary battery; a positive electrode; an anode; and a separator. In this case, in addition to the electrolyte for a lithium secondary battery, the lithium secondary battery may further include an all-solid or all-solid-state battery material capable of solidifying the electrolyte, such as a gel polymer electrolyte polymer, a polymer matrix, a pseudo-solid material, a semi-solid material, a solid polymer electrolyte, an oxide and sulfide inorganic solid electrolyte, etc.

The polymer electrolyte matrix is intended to improve the mechanical properties or high-temperature stability of the battery, and may be any one or a mixture of two or more selected from the group consisting of high-molecular polymers such as polyacrylate, polymethacrylate, polyvinylidene fluoride (PVDF), polyhexafluoro propylene (PHFP), polyethylene oxide (PEO), polypropylene oxide (PPO), polydimethyl siloxane, polyacrylonitrile (PAN), and polyvinyl chloride (PVC), PEGDME, and copolymers mixed therewith, and is not limited as long as it is a known polymer material for lithium secondary batteries.

The polymer matrix may include a crosslinking monomer for crosslinking each other. The crosslinking monomer has multiple functional groups in the monomer, and examples thereof include substances such as glutaraldehyde, tris-allylamine, and tetraallyloxyethane.

The above lithium secondary battery may use an all-solid-state electrolyte in which the electrolyte for the lithium secondary battery is converted into a solid phase.

The above positive electrode may include a positive electrode active material; a binder; a conductive material; and a current collector.

The above cathode active materials are LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _1-x Co _x O ₂ , LiNi _x Co _y Mn _z O ₂ (x+y+z=1), LiNi _x Co _{y Al z O 2} (x+y+z=1, _M is a divalent or trivalent metal or a transition metal), LiFePO ₄ , LiMnPO _{4 ,} LiCoPO _{4 ,} LiFe _{1-x M x PO 4} (M is a transition metal), a(Li ₂ MnO ₃ )· b(LiNI _x Co _y Mn _z O ₂ )(a+b=1, x+y+z=1), Li _1.2 Ni _0.13 Co _0.13-x Mn _0.54 Al _x O _2(1-y) F _2y (x, y are real numbers from 0 to 0.05 that are independent of each other), Li _1.2 Mn _(0.8-a) M _a O ₂ (M is a divalent or trivalent metal or transition metal), Li ₂ N _1-x M _x O ₃ (N is a divalent, trivalent or tetravalent metal or transition metal, M is a divalent or trivalent metal or transition metal), Li _1+x N _yz M _z O ₂ (N is Ti or Nb, M is any one selected from V, Ti, Mo or W), Li ₄ Mn _2-x M _x O ₅ (M is a metal or transition metal), Li _x M _2-x O ₂ (M is a metal or transition metal such as Ti, Zr, Nb, Mn), Li ₂ O/Li ₂ Ru _1-x M _x O ₃ (M is a metal or transition metal), but this is just one example. Any known positive electrode active material can be used, and is not necessarily limited to the examples above.

The above conductive material is used to provide conductivity to the electrode, and can be used without any special restrictions as long as it has electronic conductivity without causing a chemical change. Specific examples thereof include carbon-based materials such as graphite, carbon black, super py, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, carbon fiber, carbon nanotube, carbon nanowire, graphene, graphitized mesocarbon microbeads, fullerene, and amorphous carbon; powdered or fiber-form transition metals such as copper, nickel, aluminum, and silver; conductive whiskers such as potassium titanate; conductive metal oxides such as zinc oxide and titanium oxide; or conductive polymers such as polyphenylene derivatives, poly(3,4-ethylenedioxythiophene) (PEDOT), and polystyrene sulfonate (PSS), and copolymers thereof; but these are just examples, and any known conductive material can be used, and is not necessarily limited to the above examples.

The above binder is used to provide adhesion between the positive electrode active material and the conductive particles or between the positive electrode active material and the current collector, and any adhesive material that is chemically resistant and does not cause chemical changes may be used without any particular limitation. Specific examples thereof may include polyvinylidene fluoride (PVDF), polyimide (PI), fluoropolyimide (FPI), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), tetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), polyurethane, polyurea, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluoroelastomer, carboxymethylcellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, and starch or copolymers thereof, but this is only one example, and any known binder may be used and is not necessarily limited to the above examples.

The above current collector serves as a passage for transferring electrons from an external power source to the active material, or between the positive electrode active material and the negative electrode active material, and may use a transition metal thin film, and in particular, may use aluminum as a current collector for the positive electrode.

The above negative electrode may include a negative electrode active material; a binder; a conductive material; and a current collector.

The above negative electrode active material is a medium that reduces lithium ions to lithium and stores them, and may be any one selected from the group consisting of carbon-based materials such as natural graphite, artificial graphite (MCMB, etc.), hard carbon and soft carbon, graphene, carbon nanotubes, and fullerene; silicon-based materials such as silicon, silicon-carbon composites, silicon oxides (SiO, SiO _x ), silicon oxide-carbon composites, silica, and silicates; and lithium metal, Li ₄ Ti ₅ O ₁₂ , metal oxides (metals = Ti, V, Cr, Mn, Fe, Co, Ni, Nb, Mo, W, etc.); However, this is only an example, and any known negative electrode active material may be used, and is not necessarily limited to the above examples.

The binder and conductive material used in the above cathode are the same as those used in the above cathode, so redundant descriptions are omitted.

The above current collector has the same purpose and configuration as the positive electrode described above, but may use copper as a current collector for the negative electrode in particular.

The above-mentioned separation membrane can be used without any particular limitation as is commonly used in the art. Specific examples thereof include porous polyolefin films such as polyethylene and polypropylene; nonwoven fabrics made of polymer fibers such as polyacrylate and polyacrylonitrile; and porous polyolefin films coated with ceramic.

Hereinafter, the electrolyte for a lithium secondary battery according to the present invention and the lithium secondary battery containing the same will be described in more detail through examples. However, the following examples are merely references for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Additionally, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is solely for the purpose of effectively describing specific embodiments and is not intended to limit the invention. Furthermore, the unit of additives not specifically described in the specification may be weight percent.

[Example 1]

An electrolyte for a lithium secondary battery was prepared by adding 1 part by weight of FEC (fluoroethylene carbonate) and 0.25 part by weight of PFA (pentafluoropropionic anhydride) to 100 parts by weight of 1M LiPF ₆ in PC (propylene carbonate):DFDEC (di-(2,2,2 trifluoroethyl)carbonate) (volume ratio 3:7) electrolyte.

[Example 2]

An electrolyte for a lithium secondary battery was prepared by adding 1 part by weight of FEC and 0.25 part by weight of PFA to 100 parts by weight of 1M LiPF ₆ in EC(ethylene carbonate):EMC(ethylmethyl carbonate) (volume ratio 3:7) electrolyte.

[Example 3]

An electrolyte for a lithium secondary battery was prepared by adding 1 part by weight of PFA to 100 parts by weight of 1M LiPF ₆ in EC:EMC (volume ratio 3:7) electrolyte.

[Example 4]

An electrolyte for a lithium secondary battery was prepared by adding 1 part by weight of FEC and 1 part by weight of PFA to 100 parts by weight of 1M LiPF ₆ in PC:TFEA (2,2,2-trifluoroethyl acetate) (volume ratio 3:7) electrolyte.

[Comparative Example 1]

An electrolyte for a lithium secondary battery was prepared by adding only 1 part by weight of FEC to 100 parts by weight of 1M LiPF ₆ in PC:DFDEC (volume ratio 3:7) electrolyte.

[Comparative Example 2]

1M LiPF ₆ in EC:EMC (volume ratio 3:7) electrolyte was prepared as an electrolyte for lithium secondary batteries without additives.

[Comparative Example 3]

An electrolyte for a lithium secondary battery was prepared by adding only 1 part by weight of FEC to 100 parts by weight of 1M LiPF ₆ in EC:EMC (volume ratio 3:7) electrolyte.

[Comparative Example 4]

An electrolyte for a lithium secondary battery was prepared by adding only 2 parts by weight of FEC to 100 parts by weight of 1M LiPF ₆ in EC:EMC (volume ratio 3:7) electrolyte.

[Comparative Example 5]

An electrolyte for a lithium secondary battery was prepared by adding only 1 part by weight of FEC to 100 parts by weight of 1M LiPF ₆ in PC:TFEA (volume ratio 3:7) electrolyte.

Lithium secondary batteries were manufactured using the above Examples 1 to 4 and Comparative Examples 1 to 5 as electrolytes. Specifically, lithium secondary batteries using the above Examples 1 and 2 and Comparative Examples 1 to 3 as electrolytes were manufactured as coin batteries using a lithium metal anode, a Li-rich anode, and a PP (polypropylene) separator, and lithium secondary batteries using the above Examples 3 and 4 and Comparative Examples 4 and 5 as electrolytes were manufactured as coin batteries using a graphite anode, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811), and a PP separator.

When charging and discharging a battery, the C-rate is calculated as follows.

C-rate=(1/time to fully charge or fully discharge (hr))

[Characteristic evaluation method]

A. Charge/Discharge Performance Evaluation (Example 1 and Comparative Example 1)

Lithium secondary batteries including Example 1 and Comparative Example 1 were charged and discharged at 18C (3.3 minutes for charging) to measure electrochemical performance. At this time, the charge cut-off voltage was set to a high voltage of 4.8 V, the discharge cut-off voltage was set to 2.0 V, and the temperature was maintained at a high temperature of 45°C.

The discharge capacity and capacity retention rate at 0.2C (5 hours required for charging) shown in Table 1 below are as described below.

The discharge capacity at 0.2C is calculated as follows:

Discharge capacity (%) compared to 0.2C = (18C discharge capacity/0.2C discharge capacity)*100

The capacity retention rate is calculated as follows:

Capacity retention rate (%) = (Capacity at 100 discharges/Capacity at 1 discharge) * 100

Initial discharge capacity
(mAh/g) Discharge capacity (%) at 0.2C Capacity retention rate (%) Initial Coulombic efficiency (%) Example 1 146 55 94 81.9 Comparative Example 1 167 60 55 86.9

Referring to Table 1, when Example 1 was used, despite the harsh conditions of high voltage of 4.8 V, high rate of 18 C, and high temperature of 45 ° C, the initial capacity decreased, but the capacity retention rate was greatly improved, so that the capacity was maintained at 94% even after the 100th charge/discharge cycle, showing that Example 1 has significantly superior electrochemical performance and life characteristics compared to Comparative Example 1.

B. Interfacial resistance evaluation (Example 1 and Comparative Example 1)

Referring to FIG. 1, the interface resistance (Z) of Comparative Example 1 (non-flammable electrolyte without the additive of the invention) during the first charge/discharge cycle is 50Ω or less, which is less than about 210Ω of Example 1 (non-flammable electrolyte with the additive of the invention), but during the 100th charge/discharge cycle, the resistance of Comparative Example 1 exceeds 400Ω and increases by more than 350Ω, whereas the resistance of Example 1 is 270Ω or less, with the interface resistance increasing by only about 60Ω, confirming that the additive included in Example 1 has an excellent characteristic of suppressing changes in interface resistance.

C. Charge/Discharge Performance Evaluation (Example 2 and Comparative Examples 2 and 3)

The lithium secondary batteries including Example 2 and Comparative Examples 2 and 3 were charged and discharged at 20C (3 minutes for charging) to measure their electrochemical performance. At this time, the charge/discharge cutoff voltage was set to 2.0 to 4.8 V, and the temperature was maintained at 45°C.

The discharge capacity and capacity retention rate at 0.2C shown in Table 2 below are as described below.

The discharge capacity at 0.2C is calculated as follows:

Discharge capacity (%) compared to 0.2C = (20C discharge capacity/0.2C discharge capacity)*100

The capacity retention rate is calculated as follows:

Capacity retention rate (%) = (Capacity at n discharges/Capacity at 1 discharge) * 100

Initial discharge capacity
(mAh/g) Discharge capacity (%) at 0.2C Capacity retention rate (%) Initial Coulombic efficiency (%) Example 2 118 44 76 (400th) 82.9 Comparative Example 2 111 41 0 (360th) 84.5 Comparative Example 3 98 36 12 (400th) 82.7

Referring to Table 2, when Example 2 is used, even under harsh conditions of high voltage of 4.8 V, high rate of 20 C, and high temperature of 45 C, the initial capacity and capacity retention rate are greatly improved, and the capacity is maintained at 76% even after 400 charge/discharge cycles, showing that Example 2 has significantly superior electrochemical performance compared to Comparative Examples 2 and 3.

D. Interface resistance evaluation (Example 2 and Comparative Example 3)

Referring to Fig. 2, the interfacial resistance of the commercial electrolyte including the invention additive is smaller than that of the commercial electrolyte without the invention additive from the first charge/discharge cycle, and at the 400th charge/discharge cycle, the interfacial resistance of the commercial electrolyte without the invention additive increases significantly, whereas the commercial electrolyte including the invention additive suppresses the increase in interfacial resistance. Through this, it can be confirmed that the commercial electrolyte including the invention additive has excellent characteristics of suppressing changes in interfacial resistance.

E. Charge/Discharge Performance Evaluation (Example 3 and Comparative Example 4)

The lithium secondary batteries including Example 3 and Comparative Example 4 were charged and discharged at 3C (20 minutes for charging) to measure their electrochemical performance. At this time, the charge/discharge cutoff voltage was set to 2.7 to 4.3 V, and the temperature was maintained at 45°C.

The discharge capacity and capacity retention rate at 0.1C (10 hours required for charging) shown in Table 2 below are as described below.

The discharge capacity at 0.1C is calculated as follows:

Discharge capacity (%) compared to 0.1C = (3C discharge capacity/0.1C discharge capacity)*100

The capacity retention rate is calculated as follows:

Capacity retention rate (%) = (Capacity at n discharges/Capacity at 1 discharge) * 100

Initial discharge capacity
(mAh/g) Discharge capacity (%) at 0.1C Capacity retention rate (%) Initial Coulombic efficiency (%) Example 3 180 92 95 (200th) 82.3 Comparative Example 4 195 93 24 (100th) 77.6

Referring to Table 3, it can be seen that when Example 3 is used, the initial discharge capacity is lower than that of Comparative Example 4, but the initial coulombic efficiency is high. In addition, the capacity retention rate is very high at 95% at the 200th charge/discharge cycle, which is a significant difference from Comparative Example 4, where the capacity retention rate decreased to 24% at the 100th cycle.

F. Charge/Discharge Performance Evaluation (Example 4 and Comparative Example 5)

The lithium secondary batteries including Example 4 and Comparative Example 5 were charged and discharged at 3C (20 minutes for charging) to measure their electrochemical performance. At this time, the charge/discharge cutoff voltage was set to 2.7 to 4.3 V, and the temperature was maintained at 45°C.

The discharge capacity and capacity retention rate at 0.1C (10 hours required for charging) shown in Table 2 below are as described below.

The discharge capacity at 0.1C is calculated as follows:

Discharge capacity (%) compared to 0.1C = (3C discharge capacity/0.1C discharge capacity)*100

The capacity retention rate is calculated as follows:

Capacity retention rate (%) = (Capacity at n discharges/Capacity at 1 discharge) * 100

Initial discharge capacity
(mAh/g) Discharge capacity (%) at 0.1C Capacity retention rate (%) Initial Coulombic efficiency (%) Example 4 190 96 66 (400th) 81.7 Comparative Example 5 189 98 2(100th) 77.6

Referring to Table 4, it can be seen that when Example 4 is used, all values except the discharge capacity at 0.1C exceed those of Comparative Example 5. In particular, Example 4 is capable of 400 charge/discharge cycles and maintains a capacity of 66%, whereas Comparative Example 5 is virtually unusable as its capacity decreases to 2% of the 1st charge/discharge cycle in the 100th charge/discharge cycle.

E. Measurement of self-extinguishing time (SET, sec/g) (Examples 1 and 4 and Comparative Examples 1 and 5)

To measure the non-flammability and flame retardancy of the electrolyte, each electrolyte was ignited with a torch, and the self-extinguishing time (s) per weight (g) of electrolyte was measured after the torch was removed. If SET < 6, it can be defined as non-flammable, if 6 ≤ SET < 20, it can be defined as flame retardant, and if 20 ≤ SET, it can be defined as flammable.

SET (s/g) Flammability assessment Example 1 0 nonflammable Example 4 0 nonflammable Comparative Example 1 0 nonflammable Comparative Example 5 0 nonflammable

As shown in Table 4, Examples 1 and 4 and Comparative Examples 1 and 5 were confirmed to be non-flammable as the electrolyte itself did not ignite.

Although the present invention has been described through specific matters and limited examples as described above, these are provided only to help with the overall understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

Therefore, the idea of the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the following claims as well as the claims are considered to fall within the scope of the idea of the present invention.

Claims (7)

In an electrolyte for a lithium secondary battery containing a lithium salt and an organic solvent,
A mixture of a lithium salt and the organic solvent, comprising 0.01 to 5 parts by weight of a compound satisfying the following chemical formula 1,
The above organic solvent includes a compound satisfying chemical formula 4 and a compound satisfying chemical formula 2 or 3 below.
An electrolyte for a lithium _secondary battery, which maintains a capacity retention rate of 95% or _{more or} 66% _or more at the 400th cycle under 3C (20-minute charge/discharge) conditions from a coin battery manufactured using graphite as the negative electrode, LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) as the positive electrode, and a polypropylene separator, within 200 cycles of charge/discharge, but has a self-extinguishing time of less than 20 s·g ^-1 .
[Chemical Formula 1]

(In the above chemical formula 1,
R ₁ and R ₂ are independent C _n H _m F _(2n+1-m) (m is 0, n is an integer from 1 to 4).
[Chemical Formula 2]

(In the above chemical formula 2,
R ₁ and R ₂ are independently CH ₃ or CH _x F _3-x (x is an integer from 0 to 3),
m and n are independent integers from 1 to 3.)
[Chemical Formula 3]

(In the above chemical formula 3,
R ₁ is CH ₃ , R ₂ is CH _x F _3-x (x is 0), and m and n are independent integers from 1 to 3.)
[Chemical Formula 4]

(In the above chemical formula 4,
X ₁ and X ₂ are independent of each other, H, F, CH ₃ or CH _x F _3-x (x is an integer from 0 to 2). delete delete delete delete In the first paragraph,
A lithium secondary battery electrolyte having a concentration of the lithium salt in the electrolyte of the lithium secondary battery of 0.1 to 20 M. A lithium secondary battery comprising an electrolyte for a lithium secondary battery according to any one of claims 1 to 6; a positive electrode; an negative electrode; and a separator.