technology field
[One]
Cross-citation with related application(s)
[2]
This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0149269 dated November 10, 2020 and Korean Patent Application No. 10-2021-0152275 dated November 8, 2021, and All material disclosed in the literature is incorporated as part of this specification.
[3]
[4]
technology field
[5]
The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery including an additive capable of forming a robust SEI film and a lithium secondary battery including the same.
background art
[6]
As personal IT devices and computer networks develop due to the development of the information society, and as a result, the overall society's dependence on electrical energy increases, the development of technology for efficiently storing and utilizing electrical energy is required.
[7]
Secondary batteries can be miniaturized enough to be applied to personal IT devices, etc., and can be applied to electric vehicles, power storage devices, etc., so interest is emerging as the most suitable technology for various purposes. Among secondary batteries, a lithium ion battery (LIB), which is a battery system with high energy density, is in the limelight and is currently applied to various devices.
[8]
A lithium ion battery generally consists of a positive electrode including a positive electrode active material made of a transition metal oxide containing lithium, a negative electrode including a negative electrode active material capable of storing lithium ions, an electrolyte serving as a medium for delivering lithium ions, and a separator. do.
[9]
On the other hand, lithium, graphite, and silicon-based negative electrodes are representative active materials currently used in commercial lithium-ion batteries, and charge and discharge capacities through electrochemical oxidation-reduction reactions at 0.2 V and 0.5 V (vs. (Li/Li+)) or less, respectively. expresses However, since the operating voltage range of lithium, graphite, and silicon-based negative electrodes is lower than the electrochemical stability window of the organic electrolyte, the organic electrolyte becomes electrochemically unstable in these operating voltage ranges. As a result, reduction decomposition of the electrolyte occurs in advance, and a passivation layer, that is, a solid electrolyte decomposition product film (solid electrolyte interphase (SEI)), which is a reduction decomposition product of the electrolyte, is formed on the electrode surface.
[10]
This SEI is a passivation layer with high lithium ion conductivity but low electronic conductivity, which not only suppresses additional electrolyte reduction decomposition, but also transmits lithium ions but suppresses the transmission of electrons, which enables driving of lithium ion batteries. has
[11]
However, when exposed to high temperatures for a long time, the SEI film is damaged and the passivation ability is lost. At this time, additional electrolyte decomposition occurs, consuming lithium and electrons inside the cell, causing degradation of the cell's electrochemical performance, or lowering the temperature inside the cell. high, causing thermal runaway.
[12]
Accordingly, there is a demand for development of a novel electrolyte composition capable of forming a solid passivation layer on the surfaces of the anode and cathode.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[13]
The present invention is to solve the above problems, to provide a non-aqueous electrolyte solution for a lithium secondary battery containing an additive capable of forming a solid passivation film on the surface of the positive electrode and the negative electrode.
[14]
In addition, the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte solution for the lithium secondary battery.
means of solving the problem
[15]
According to one embodiment, the present invention provides a non-aqueous electrolyte solution for a lithium secondary battery including a lithium salt, an organic solvent, and a compound represented by Formula 1 below.
[16]
[Formula 1]
[17]

[18]
In Formula 1,
[19]
R is an alkylene group having 1 to 4 carbon atoms,
[20]
R 1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine.
[21]
[22]
According to another embodiment, the present invention provides a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator interposed between the negative electrode and the positive electrode; And it provides a lithium secondary battery comprising the non-aqueous electrolyte for lithium secondary batteries of the present invention.
Effects of the Invention
[23]
Since the non-aqueous electrolyte solution for a lithium secondary battery of the present invention includes the compound represented by Chemical Formula 1 containing at least one nitrogen element and at least one fluorine element in its molecular structure as an additive, it is possible to form a solid passivation film on the surface of the positive electrode or negative electrode. there is. Accordingly, a lithium secondary battery having improved high-temperature storage stability and high-temperature capacity characteristics may be implemented.
Mode for Carrying Out the Invention
[24]
First, prior to describing the present invention, the terms or words used in this specification and claims should not be construed as being limited to common or dictionary meanings, and the inventors should explain their own invention in the best way. Based on the principle that the concept of risk terms can be properly defined, they must be interpreted as meanings and concepts consistent with the technical spirit of the present invention.
[25]
Meanwhile, terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.
[26]
In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, number, step, component, or combination thereof, but one or more other features or It should be understood that the presence or addition of numbers, steps, components, or combinations thereof is not precluded.
[27]
In this specification, "%" means % by weight unless expressly indicated otherwise.
[28]
Prior to explaining the present invention, in the description of "carbon number a to b" in the specification, "a" and "b" mean the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms.
[29]
In addition, in this specification, unless otherwise defined, "substitution" means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, for example, an alkyl group having 1 to 5 carbon atoms or a fluorine element. means that it has been replaced by
[30]
[31]
Hereinafter, the present invention will be described in more detail.
[32]
Recently, as the lithium ion battery market expands, there is a demand for technology development capable of securing battery performance and stability in a higher temperature range (60 ° C to 100 ° C) than the existing high-temperature environment (45 ° C to 60 ° C). . For example, SEI, which is a passivation film, has the disadvantage of losing its passivation ability due to its own thermal decomposition at a high temperature of 85°C or higher, or being damaged by materials produced by thermal decomposition of lithium salt, while maintaining passivation ability at 60°C. When the SEI is deteriorated, a film is formed (recovered) while additional electrolyte reduction decomposition occurs on the electrode surface exposed by receiving lithium and electrons from the electrode. This recovery process of the SEI film continues until lithium and electrons in the electrode are completely consumed. As such, if the damage and recovery of the SEI film are continuously repeated at high temperatures, the thickness of the film gradually grows, which causes an increase in polarization of the cell and serious degradation of the charge / discharge capacity, thereby degrading the electrochemical performance of the battery. let it
[33]
In order to solve these problems, the present invention provides a non-aqueous electrolyte solution for a lithium secondary battery containing an additive capable of forming a stable film containing a nitrogen element and/or a fluorine element on the surface of the positive electrode and the negative electrode, and a lithium secondary battery including the same. want to do
[34]
[35]
Non-aqueous electrolyte for lithium secondary battery
[36]
The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery comprising a lithium salt, an organic solvent, and a compound represented by Formula 1 below.
[37]
[Formula 1]
[38]

[39]
In Formula 1,
[40]
R is an alkylene group having 1 to 4 carbon atoms,
[41]
R 1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine.
[42]
[43]
(1) lithium salt
[44]
As the lithium salt, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, for example, including Li + as a cation and F - , Cl - , Br - , I - , NO 3 - as an anion , N(CN) 2 - , BF 4 - , ClO 4 - , B 10 Cl 10 - , AlCl 4 - , AlO 2 - , PF 6 - , CF 3 SO 3 - , CH 3CO 2 - , CF 3 CO 2 - , AsF 6 - , SbF 6 - , CH 3 SO 3 - , (CF 3 CF 2 SO 2 ) 2 N - , (CF 3 SO 2 ) 2 N - , (FSO 2 ) 2 N - , BF 2 C 2 O 4 - , BC 4 O 8 - , PF 4 C 2 O 4 - , PF 2 C 4 O 8 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3) 6 P - , C 4 F 9 SO 3 - , CF 3 CF 2 SO 3 - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - , CF 3 (CF 2 ) 7 SO 3 - and SCN -It may include at least one selected from the group consisting of.
[45]
Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiB 10 Cl 10 , LiAlCl 4 , LiAlO 2 , LiPF 6 , LiCF 3 SO 3 , LiCH 3 CO 2 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiCH 3 SO 3 , LiFSI (Lithium bis(fluorosulfonyl)imide, LiN(SO 2 F) 2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO 2 CF 2 CF 3 ) 2 and LiTFSI (lithium bis(trifluoromethanesulfonyl) imide, LiN(SO 2 CF 3 ) 2 ) a single material or two or more selected from the group consisting of In addition to these, lithium salts commonly used in electrolyte solutions of lithium secondary batteries may be used without limitation.
[46]
The lithium salt may be appropriately changed within a generally usable range, but in order to obtain an optimum effect of forming a film for preventing corrosion on the surface of the electrode, it is included in the electrolyte solution at a concentration of 0.8 M to 4.0 M, specifically 1.0 M to 3.0 M. can
[47]
If the concentration of the lithium salt is less than 0.8 M, the mobility of lithium ions decreases, so the effect of improving low-temperature output and cycle characteristics during high-temperature storage is insignificant, and if the concentration of the lithium salt exceeds 4.0 M, the viscosity of the non-aqueous electrolyte becomes excessive. As a result, the impregnability of the non-aqueous electrolyte may decrease, and the effect of forming a film may decrease.
[48]
[49]
(2) organic solvent
[50]
As the organic solvent, various organic solvents commonly used in lithium electrolytes may be used without limitation. For example, the organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof.
[51]
The cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can easily dissociate lithium salts in the electrolyte. It may contain at least one organic solvent selected from the group consisting of carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and vinylene carbonate, among which ethylene carbonate And it may include at least one or more of propylene carbonate (PC).
[52]
In addition, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and typical examples thereof include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and ethylmethyl carbonate ( EMC), at least one organic solvent selected from the group consisting of methylpropyl carbonate and ethylpropyl carbonate may be used, and specifically, ethylmethyl carbonate (EMC) may be included.
[53]
The cyclic carbonate organic solvent and the linear carbonate organic solvent may be included in a volume ratio of 1:9 to 5:5, specifically 2:8 to 3:7.
[54]
In addition, the organic solvent is a linear ester-based organic solvent having a low melting point and high stability at high temperature and/or a cyclic carbonate-based organic solvent and/or a cyclic carbonate-based organic solvent in order to prepare an electrolyte solution having high ionic conductivity. An ester-based organic solvent may be further included.

We claims:

[Claim 1]
A non-aqueous electrolyte solution for a lithium secondary battery comprising a lithium salt, an organic solvent, and a compound represented by Formula 1 below. [Formula 1] In Formula 1, R is an alkylene group having 1 to 4 carbon atoms, and R 1 is an alkyl group having 1 to 5 carbon atoms substituted with at least one fluorine.
[Claim 2]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein in Formula 1, R is an alkylene group having 2 to 4 carbon atoms, and R 1 is an alkyl group having 1 to 4 carbon atoms substituted with at least one fluorine.
[Claim 3]
The non-aqueous electrolyte solution for a lithium secondary battery as set forth in claim 2, wherein in Formula 1, R 1 is an alkyl group having 1 to 3 carbon atoms substituted with at least one fluorine.
[Claim 4]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the compound represented by Formula 1 is a compound represented by Formula 1a below. [Formula 1a]
[Claim 5]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, wherein the compound represented by Formula 1 is included in an amount of 0.01% to 5% by weight based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.
[Claim 6]
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 5, wherein the compound represented by Formula 1 is included in an amount of 0.5% to 5% by weight based on the total weight of the non-aqueous electrolyte solution for a lithium secondary battery.
[Claim 7]
The method according to claim 1, wherein the non-aqueous electrolyte for a lithium secondary battery is a halogen-substituted or unsubstituted carbonate-based compound, a sultone-based compound, a sulfate-based compound, a phosphate-based or phosphite-based compound, a borate-based compound, a nitrile-based compound, or an amine-based compound. , A non-aqueous electrolyte solution for a lithium secondary battery further comprising at least one other additive selected from the group consisting of silane-based compounds and lithium salt-based compounds.
[Claim 8]
a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator interposed between the negative electrode and the positive electrode; And a lithium secondary battery comprising the non-aqueous electrolyte for a lithium secondary battery of claim 1.
[Claim 9]
The method according to claim 8, wherein the cathode active material is lithium containing at least one metal selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe) and aluminum (Al) and lithium secondary battery.
[Claim 10]
The lithium secondary battery of claim 8 , wherein the anode active material includes at least one of a carbon-based anode active material and a silicon-based anode active material.