Non-aqueous electrolyte and lithium secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte comprising a lithium salt, an organic solvent, a compound represented by Chemical Formula 1 as a first additive, and a compound represented by Chemical Formula 2 or Chemical Formula 3 as a second additive. In Chemical Formula 1, R 1 is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, SO 2 R’, and COR’, where R’ is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and R 2 and R 3 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. In Chemical Formula 2, R is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R 4 to R 6 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group. In Chemical Formula 3, R 7 is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, and R 8 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0171006, filed on December 8, 2022, and all the contents disclosed in the documents of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery including the same.

Background Art

[0003] In recent years, the application fields of lithium secondary batteries have rapidly expanded not only to power supply for electronic devices such as electric, electronic, communication, and computer devices, but also to power storage and supply for large-area devices such as automobiles and power storage devices. Along with this, the demand for secondary batteries with high capacity, high output, and high stability has been increasing.

[0004] Particularly, in lithium secondary batteries for automotive applications, high capacity, high output, and long-term life characteristics are important. For increasing the capacity of secondary batteries, a positive electrode active material with a high nickel content having high energy density but low stability may be used, or the secondary battery may be driven at a high voltage.

[0005] However, when driving a secondary battery under the above conditions, as charge and discharge proceed, due to side reactions caused by deterioration of the electrolyte, the film formed on the surface of the positive / negative electrode or the structure of the electrode surface deteriorates, and transition metal ions may be eluted from the surface of the positive electrode. In this way, the eluted transition metal ions are electrodeposited on the negative electrode, reducing the passivation ability of the SEI, resulting in a problem that the negative electrode deteriorates.

[0006] Such a deterioration phenomenon of the secondary battery tends to accelerate when the potential of the positive electrode increases or the battery is exposed to high temperature, and due to the deterioration phenomenon, there is a problem that the cycle characteristics of the secondary battery deteriorate.

[0007] In addition, when a lithium secondary battery is used continuously for a long time or left at a high temperature, a so-called swelling phenomenon occurs where gas is generated and the thickness of the battery increases. The amount of gas generated at this time is known to depend on the state of such SEI.

[0008] Therefore, in order to solve such problems, research and development have been conducted on a method that can suppress the elution of metal ions in the positive electrode, form a stable SEI film on the negative electrode, reduce the swelling phenomenon of the secondary battery, and enhance the stability at high temperatures.

Summary of the Invention

Problems to be Solved by the Invention

[0009] As a result of conducting extensive research to solve the above problems, the present invention aims to provide a non-aqueous electrolyte that can suppress the degradation of the positive electrode, reduce the side reaction between the positive electrode and the electrolyte, form a stable SEI film on the negative electrode, and enhance the stability at high temperatures.

[0010] That is, the present invention aims to provide a lithium secondary battery in which the high-temperature cycle characteristics, high-temperature storage characteristics, and thermal stability are improved and various performances are enhanced by including the non-aqueous electrolyte.

Means for Solving the Problems

[0011] To achieve the above object, an embodiment of the present invention provides a non-aqueous electrolyte containing a lithium salt, an organic solvent, a compound represented by the following Chemical Formula 1 as a first additive, and a compound represented by the following Chemical Formula 2 or Chemical Formula 3 as a second additive.

[0012]

Chem.

[0013] In the above Chemical Formula 1, R 1is an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, SO 2 is any one selected from the group consisting of R’ and COR’, where R’ is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and R 2 and R 3 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms.

[0014] [Chemical formula]

[0015] In Chemical Formula 2, R is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R 4 ~R 6 are each independently any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group.

[0016] [Chemical formula]

[0017] In Chemical Formula 3, R 7 is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, and R 8 is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

[0018] Also, an embodiment of the present invention provides a lithium secondary battery including the non-aqueous electrolyte. [Advantages of the Invention]

[0019] The compound of Chemical Formula 1 provided as the first additive of the present invention is an oxazolidinone compound, which easily forms a film while the cyclic structure is cleaved on the surfaces of the positive electrode and the negative electrode. Specifically, since the electron density of carbon, which has a lower electronegativity than nitrogen and oxygen in the oxazolidinone ring, is low, it can be easily reduced at the negative electrode to form a film. Conversely, at the positive electrode, during charging, the oxidation number of the transition metal of the positive electrode active material increases, and the oxygen of C=O in the oxazolidinone ring strongly interacts with the positive electrode, so that the cyclic structure can be cleaved to easily form a film. Since the oxazolidinone ring structure is cleaved to form a radical form and causes an additional cross-linking reaction, a strong and stable film can be formed. In addition, oxygen and nitrogen in the oxazolidinone ring structure have non-bonding electron pairs, so when lithium ions are lithiated / delithiated at the positive electrode / negative electrode, a film with high lithium mobility is formed. Therefore, the first additive of the present invention can suppress the decrease in the passivation ability of SEI at high temperatures, prevent the deterioration of the negative electrode, and improve the performance of the lithium secondary battery.

[0020] The compound of Chemical Formula 2 or Chemical Formula 3 provided as the second additive of the present invention contains a propargyl group in the molecule, which helps in improving the high-temperature durability. The SEI film formed by the negative electrode reduction reaction of the compound of Chemical Formula 2 or Chemical Formula 3 contains a propargyl group, and the propargyl group serves as a cross-linking site in the SEI, enabling an additional reaction. As the additional cross-linking reaction proceeds, a strong SEI film is formed, which is effective in suppressing the performance degradation due to the negative electrode electrodeposition of the transition metal eluted from the positive electrode. In addition, the cyclic carbonate functional group and imidazole functional group contained in the additive of Chemical Formula 2 or Chemical Formula 3 effectively suppress side reactions and the deterioration of the positive electrode by forming a stable CEI, improve the performance, and can reduce the elution of the transition metal that may occur during high-voltage charging. That is, the compound of Chemical Formula 2 or Chemical Formula 3 provided as the second additive for the non-aqueous electrolyte of the present invention can form a stable ion-conductive film on the surfaces of the positive / negative electrodes.

[0021] Therefore, when the non-aqueous electrolyte of the present invention containing the first additive and the second additive is used, the radical generated while the ring structure of the first additive is cleaved promotes the film-forming reaction of the second additive. The film formed by the interaction between the first additive and the second additive has an oxazolidinone, imidazole, cyclic carbonate structure, or a structure derived therefrom between the films based on the aliphatic alkyl group, and a film form excellent in lithium ion transfer characteristics is formed, thereby improving various performances such as charge-discharge characteristics and output characteristics of the lithium secondary battery. The film formed by the interaction between the first additive and the second additive is excellent in oxidation resistance, and thus can suppress side reactions occurring in the positive / negative electrode films even in an acidic atmosphere of the electrolyte. In addition, the film formed by the interaction between the first additive and the second additive is also excellent in durability against the volume expansion of the negative electrode occurring during charge and discharge. Therefore, the non-aqueous electrolyte of the present invention can form a stable and highly durable electrode-electrolyte interface even at high temperatures and can suppress unnecessary electrolyte decomposition side reactions, thereby realizing a lithium secondary battery with improved various performances.

Embodiments for Carrying Out the Invention

[0022] Terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. The inventor should interpret them in accordance with the meaning and concept consistent with the technical idea of the present invention in accordance with the principle that the concept of the terms can be appropriately defined in order to explain his invention in the best way.

[0023] In this specification, terms such as "comprising", "including", or "having" are intended to specify the presence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood not to preclude the presence or addition possibility of one or more other features, numbers, steps, components, or combinations thereof in advance.

[0024] In addition, in this specification, in the description of "carbon number a to b", "a" and "b" mean the number of carbon atoms contained in a specific functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "an alkylene group having 1 to 5 carbon atoms" means an alkylene group containing 1 to 5 carbon atoms, that is, -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 (CH 3 )CH-, -CH(CH 3 )CH 2 -, and -CH(CH 3 )CH 2 CH 2 - and the like.

[0025] In addition, in this specification, the term "alkylene group" means a branched or unbranched divalent saturated hydrocarbon group.

[0026] In addition, in this specification, any alkyl group may or may not be substituted. The term "substitution" means that, unless otherwise defined, at least one or more hydrogens bonded to carbon are substituted with an element other than hydrogen. For example, it means being substituted with an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, a heterocycloalkenyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, a nitro group, a nitrile group, or the like.

[0027] Hereinafter, the present invention will be described in more detail.

[0028] Non-aqueous electrolyte The non-aqueous electrolyte according to the present invention may contain a lithium salt, an organic solvent, a compound of the following Chemical Formula 1 as a first additive, and a compound of the following Chemical Formula 2 or Chemical Formula 3 as a second additive.

[0029] The non-aqueous electrolyte according to the present invention contains a compound represented by the following Chemical Formula 1 as a first additive. The compound of the following Chemical Formula 1 is an oxazolidinone-based compound, and a film is easily formed while the cyclic structure is cleaved on the surfaces of the positive electrode and the negative electrode. Specifically, since the electron density of carbon, which has a lower electronegativity than nitrogen and oxygen in the oxazolidinone ring, is low, it is easily reduced at the negative electrode to form a film. Conversely, at the positive electrode, the oxidation number of the transition metal of the positive electrode active material increases during charging, and the oxygen of C=O in the oxazolidinone ring strongly interacts with the positive electrode, so that the cyclic structure is cleaved and a film can be easily formed. Since the oxazolidinone ring structure is cleaved to become a radical form and causes an additional cross-linking reaction, a strong and stable film can be formed. In addition, since oxygen and nitrogen in the oxazolidinone ring structure have unshared electron pairs, when lithium ions are lithiated / delithiated at the positive electrode / negative electrode, a film with high lithium mobility is formed. Therefore, the first additive of the present invention can suppress a decrease in the passivation ability of SEI at high temperatures, prevent deterioration of the negative electrode, and improve the performance of the lithium secondary battery.

[0030]

Chemical formula

[0031] In the above Chemical Formula 1, R 1 may be any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, SO 2 R’ and COR’. Preferably, the R 1Those substituted with fluorine are preferred. In this case, an organic-inorganic composite film can be formed, and a strong and durable film can be formed. A film containing an organic component has excellent lithium transfer characteristics but is likely to cause side reactions in an acidic electrolyte atmosphere. An inorganic film suppresses side reactions in an acidic atmosphere but has poor lithium transfer characteristics. Therefore, when forming an organic-inorganic composite film, various characteristics of the lithium secondary battery are maximized.

[0032] Said R' may be any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine.

[0033] In the chemical formula 1, R 2 and R 3 may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Preferably, both R 2 and R 3 may be H.

[0034] Specifically, the compound of the chemical formula 1 may be any one of the compounds represented by the following chemical formulas 1-1 to 1-6.

[0035]

Chem.

[0036]

Chem.

[0037]

Chem.

[0038]

Chem.

[0039] [Chem.]

[0040] [Chem.]

[0041] The non-aqueous electrolyte according to the present invention contains, as a second additive, a compound represented by the following Chemical Formula 2 or Chemical Formula 3. Since the compound of Chemical Formula 2 or Chemical Formula 3 contains a propargyl group, it is easily reduced on the surface of the negative electrode and can easily form a film on the surface of the negative electrode. Such a film has higher stability than the SEI film formed by the reductive decomposition of a general electrolyte, has low electron conductivity, suppresses the decomposition reaction of an additional electrolyte, and has the advantage of being hardly damaged by the volume change of the negative electrode. That is, by using the compound of Chemical Formula 2 or Chemical Formula 3 as an additive for the electrolyte, the stability of the interface between the negative electrode and the electrolyte can be ensured.

[0042] Since the compound of Chemical Formula 2 contains a propargyl group having a triple bond known to have metal ion adsorption performance and an oxygen atom, the propargyl group separated by the bond cleavage of the nitrogen (N) atom and the carbon (C) atom of the imidazole group adsorbs metal foreign substances such as Fe, Co, Mn, and Ni eluted from the positive electrode during high-voltage charging, and thus the negative electrode deterioration phenomenon caused by the electrodeposition of these metal foreign substances on the surface of the negative electrode can be effectively suppressed. In addition, since the lone pair of the nitrogen (N) atom of the imidazole group of the compound represented by Chemical Formula 2 reacts with an alkyl carbonate which is a decomposition product of ethylene carbonate (EC) used as an organic solvent and is reduced on the surface of the negative electrode, a stable ion conductive film can be formed on the surface of the negative electrode. Therefore, not only can the additional electrolyte decomposition reaction during the charge and discharge process be suppressed, but also the occlusion and release of lithium ions from the negative electrode can be smoothed during overcharging or high-temperature storage, and the cycle life characteristics and high-temperature storage performance of the secondary battery can be improved.

[0043]

Chem.

[0044] In the chemical formula 2 above, R is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine, and R 4 ~R 6 may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group.

[0045] Specifically, the compound of chemical formula 2 of the present invention may be a compound of the following chemical formula 2-1.

[0046]

Chem.

[0047] The compound of chemical formula 3 contains an ester functional group and an unsaturated hydrocarbon group in its molecular structure, is decomposed prior to other components of the electrolyte during the initial charging process of the secondary battery, and forms a film mainly composed of a carbon-oxygen single bond (C-O) or carbon-oxygen double bond (C=O)-based compound on the surface of the negative electrode. Further, since the compound of chemical formula 3 contains a propargyl group, it is easily reduced on the surface of the negative electrode and can easily form a film on the surface of the negative electrode. Such a film has higher stability than the SEI film formed by the reduction decomposition of a general electrolyte, has low electron conductivity and suppresses the decomposition reaction of additional electrolyte, and has the advantage of being less damaged by the volume change of the negative electrode.

[0048]

Chem.

[0049] In the chemical formula 3 above, R 7 is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, and preferably may be an alkylene group having 1 to 5 carbon atoms.

[0050] In the above Chemical Formula 3, R 8 may be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

[0051] The compound of Chemical Formula 3 may be a compound of the following Chemical Formula 3-1.

[0052]

Chemical Formula

[0053] In the above Chemical Formula 3-1, n is a natural number from 1 to 8, preferably a natural number from 1 to 5, and most preferably a natural number from 1 to 3.

[0054] 8 In the above Chemical Formula 3-1, R

[0055] Specifically, the compound of Chemical Formula 3 of the present invention may be a compound of the following Chemical Formula 3-2.

[0056]

Chemical Formula

[0057] When the non-aqueous electrolyte of the present invention containing the first additive and the second additive is used, the coating formation reaction of the second additive is promoted by radicals generated while the ring structure of the first additive is cleaved. The coating formed by the interaction between the first additive and the second additive has an oxazolidinone, imidazole, cyclic carbonate structure, or a structure resulting therefrom between the coatings based on aliphatic alkyl groups, and a coating morphology excellent in lithium ion transfer characteristics is formed, thereby improving various performances such as charge-discharge characteristics and output characteristics of the lithium secondary battery. The coating formed by the interaction between the first additive and the second additive is excellent in oxidation resistance, so that side reactions occurring in the coatings of the positive / negative electrodes can be suppressed even in an acidic atmosphere of the electrolyte. In addition, the coating formed by the interaction between the first additive and the second additive is also excellent in durability against volume expansion of the negative electrode occurring during charge and discharge. Therefore, the non-aqueous electrolyte of the present invention can form a stable and highly durable electrode-electrolyte interface even at high temperatures and can suppress unnecessary electrolyte decomposition side reactions, thus realizing a lithium secondary battery with improved various performances.

[0058] In the non-aqueous electrolyte according to the present invention, the first additive may be contained in an amount of 0.01 part by weight to 10 parts by weight, or 0.01 part by weight to 5 parts by weight, preferably 0.05 part by weight to 3.0 parts by weight, more preferably 0.10 part by weight to 2.0 parts by weight, based on 100 parts by weight of the non-aqueous electrolyte. When the content of the first additive satisfies the above range, the effect of forming a coating on the negative electrode is sufficient, and there is an effect of excellent life characteristics and high-temperature storage characteristics at high temperatures.

[0059] In the non-aqueous electrolyte according to the present invention, the second additive may be contained in an amount of 0.01 part by weight to 5 parts by weight, preferably 0.05 part by weight to 3.0 parts by weight, more preferably 0.10 part by weight to 2.5 parts by weight, based on 100 parts by weight of the non-aqueous electrolyte. When the content of the second additive satisfies the above range, the effect of forming a coating on the negative electrode is sufficient, and there is an effect of excellent life characteristics and high-temperature storage characteristics at high temperatures.

[0060] In the non-aqueous electrolyte of the present invention, the first additive and the second additive may be contained in a weight ratio of 1:0.001 to 1:500, or a weight ratio of 1:0.002 to 1:500, preferably a weight ratio of 1:0.01 to 1:300, and most preferably a weight ratio of 1:0.02 to 1:250. When the above range is satisfied, the elasticity of the SEI film becomes an appropriate range, and the SEI film can be firmly maintained during charge and discharge or at high temperature.

[0061] The non-aqueous electrolyte according to the present invention may contain a lithium salt. The lithium salt is used as an electrolyte salt in a lithium secondary battery and is used as a mediator for transmitting ions. Usually, as the lithium salt, for example, as a cation, Li + is included, and as an anion, F - , Cl - , Br - , I - , NO 3 - , N(CN) 2 - , BF 4 - , ClO 4 - , B 10 Cl 10 - , AlCl 4 - , AlO 2 - , PF 6 - , CF 3 SO 3 - , CH 3 CO 2 - , CF 3 CO 2 - , AsF 6 - , SbF 6 - , CH 3 SO 3 - , (CF 3 CF 2 SO 2 ) 2 N - , (CF3 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 - 、およびSCN - At least one selected from the group consisting of

[0062] Specifically, the lithium salt may include a single substance or a mixture of two or more selected from the group consisting of LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiB 10 Cl 10 , LiAlCl 4 , LiAlO 2 , LiPF 6 , LiSO 3 CF 3 , LiCO 2 CH 3 , LiCO 2 CF 3 , LiAsF 6 , LiSbF 6 , LiSO 3 CH 3 , LiN(SO 2 F) 2 (lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO 2 CF 2 CF 3 ) 2 (lithium bis(perfluoroethanesulfonyl)imide; LiBETI), and LiN(SO 2 CF 3 ) 2 (lithium bis(trifluoromethanesulfonyl)imide; LiTFSI). In addition to these, lithium salts usually used in the electrolyte of lithium secondary batteries can be used without limitation.

[0063] The lithium salt can be appropriately changed within the range that can be usually used. However, in order to obtain the effect of forming a coating for preventing corrosion of the optimal electrode surface, it may be contained in the electrolyte at a concentration of 0.5 M to 5.0 M, preferably 1.0 M to 3.0 M, more preferably 1.2 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate and the electrolyte impregnation property can be improved.

[0064] The non-aqueous electrolyte according to the present invention may contain an organic solvent. The organic solvent may contain at least one or more organic solvents selected from the group consisting of cyclic carbonate-based organic solvents, linear carbonate-based organic solvents, linear ester-based organic solvents, and cyclic ester-based organic solvents.

[0065] The additive according to the present invention is particularly effective when using a cyclic carbonate solvent. When using a conventional electrolyte additive together with a cyclic carbonate solvent, the SEI film formed by the decomposition of the cyclic carbonate solvent is difficult to maintain due to the volume change of the negative electrode occurring during the progress of the cycle, and there is a problem that the decomposition of the solvent continues. As a result, there is a problem that the ionic conductivity of the electrolyte decreases and the cycle characteristics deteriorate. However, when using a combination of the additive according to the present invention together with a cyclic carbonate solvent, a strong SEI film can be formed, and there is an effect that the cycle characteristics are maintained high.

[0066] The cyclic carbonate-based organic solvent is a high-viscosity organic solvent and is an organic solvent having a high dielectric constant and easily dissociating lithium salts in the electrolyte. Specific examples thereof may include at least one or more organic solvents selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. Among them, it may contain fluoroethylene carbonate (FEC).

[0067] In addition, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant. Representative examples thereof include at least one or more organic solvents selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate. Among them, it may contain diethyl carbonate (DEC).

[0068] In addition, in order to produce an electrolyte having a high ionic conductivity, the organic solvent may further contain at least one or more ester-based organic solvents selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents in at least one or more carbonate-based organic solvents selected from the group consisting of the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent.

[0069] Specific examples of such linear ester-based organic solvents include at least one or more organic solvents selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0070] In addition, examples of the cyclic ester-based organic solvent include at least one or more organic solvents selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0071] On the other hand, the organic solvent may be additionally used as needed without restricting the organic solvents commonly used in non-aqueous electrolytes. For example, it may further contain at least one or more organic solvents such as ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0072] As the ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these can be used, but it is not limited thereto.

[0073] The glyme-based solvent has a high dielectric constant and a low surface tension compared to linear carbonate-based organic solvents, and is a solvent with little reactivity with metals. It may contain at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraethylene glycol dimethyl ether (TEGDME), but is not limited thereto.

[0074] The nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, but is not limited thereto.

[0075] In addition, in order to prevent the non-aqueous electrolyte from being decomposed in a high-output environment and causing the collapse of the negative electrode, or to further improve the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, battery expansion suppression effect at high temperature, etc., the non-aqueous electrolyte may further contain a known electrolyte additive as needed.

[0076] Such other electrolyte additives may include, as representative examples thereof, at least one or more additives for forming a SEI film selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0077] Examples of the cyclic carbonate compound include vinylene carbonate (VC) or vinyl ethylene carbonate.

[0078] Examples of the halogen-substituted carbonate compound include fluoroethylene carbonate (FEC).

[0079] Examples of the sultone compound include at least one or more compounds selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethenesultone, 1,3-propenesultone (PRS), 1,4-butenesultone, and 1-methyl-1,3-propenesultone.

[0080] Examples of the sulfate compound include ethylene sulfate (Ethylene Sulfate; Esa), trimethylene sulfate (Trimethylene sulfate; TMS), or methyl trimethylene sulfate (Methyl trimethylene sulfate; MTMS).

[0081] Examples of the phosphate compound include one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(2,2,2-trifluoroethyl)phosphite.

[0082] Examples of the borate compound include tetraphenylborate, lithium difluoro(oxalate)borate (LiODFB), and lithium bisoxalate borate (LiBOB). 2 O 4 ) 2 (LiBOB).

[0083] Examples of the nitrile compound include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0084] Examples of the benzene compound include fluorobenzene, examples of the amine compound include triethanolamine or ethylenediamine, etc., and examples of the silane compound include tetravinylsilane.

[0085] The lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples include lithium difluorophosphate (LiDFP), LiPO 2 F 2 , or LiBF 4 etc.

[0086] When such other electrolyte additives further include a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), ethylene sulfate (Esa), and lithium difluorophosphate (LiDFP), a stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery, the generation of gas that may be generated by the decomposition of the electrolyte at high temperature can be suppressed, and the high-temperature stability of the secondary battery can be improved.

[0087] On the other hand, two or more of the other electrolyte additives may be used in combination, and they may be contained in an amount of 0.050% by weight to 20% by weight, specifically 0.10% by weight to 15% by weight, preferably 0.30% by weight to 10% by weight, based on the total weight of the non-aqueous electrolyte. When the content of the other electrolyte additives satisfies the above range, a more excellent effect of improving ion conductivity and cycle characteristics can be obtained.

[0088] Lithium secondary battery The present invention also provides a lithium secondary battery including the non-aqueous electrolyte.

[0089] Specifically, the lithium secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the aforementioned non-aqueous electrolyte.

[0090] At this time, the lithium secondary battery of the present invention can be manufactured by a conventional method known in the art. For example, after forming an electrode assembly in which a positive electrode, a negative electrode, and a separator are sequentially laminated between the positive electrode and the negative electrode, the electrode assembly is inserted into the inside of a battery case, and the non-aqueous electrolyte according to the present invention is injected to manufacture it.

[0091] (1) Positive electrode The positive electrode can be manufactured by coating a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, a solvent, etc. on a positive electrode current collector.

[0092] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used.

[0093] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (for example, LiMnO 2 、LiMn 2 O 4 etc.), a lithium-cobalt-based oxide (for example, LiCoO 2 etc.), a lithium-nickel-based oxide (for example, LiNiO 2 etc.), a lithium-nickel-manganese-based oxide (for example, LiNi 1-Y Mn Y O 2 (where 0 < Y < 1), LiMn 2-Z Ni Z O 4 (where 0 < Z < 2) etc.), a lithium-nickel-cobalt-based oxide (for example, LiNi 1-Y1 Co Y1 O 2 (where 0 < Y1 < 1) etc.), a lithium-manganese-cobalt-based oxide (for example, LiCo 1-Y2 Mn Y2 O 2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O 4 (where 0 < Z1 < 2) etc.), a lithium-nickel-manganese-cobalt-based oxide (for example, Li(Ni p Co q Mn r )O 2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O 4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2) etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Ni p2 Co q2 Mn r2 M s2 )O 2(Here, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of independent elements, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.) etc. are included, and any one or two or more of these compounds may be contained.

[0094] Among them, from the viewpoint of being able to enhance the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO 2 , LiMnO 2 , LiNiO 2 , lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O 2 , Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 , Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 , Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 , and Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O 2 etc.) etc. may be used, and any one or two or more of these mixtures may be used.

[0095] Among them, from the viewpoint of being able to enhance the capacity characteristics of the battery most, a positive electrode active material having a nickel content of 80 atm% or more can be used. For example, the lithium transition metal oxide may include those represented by the following Chemical Formula 4.

[0096] [Chemical Formula 4] Lix Ni a Co b M 1 c M 2 d O 2

[0097] In Chemical Formula 4, the M 1 is one or more selected from Mn and Al, and may preferably be Mn, or a combination of Mn and Al.

[0098] M 2 may be one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb.

[0099] The x represents the atomic fraction of lithium in the lithium transition metal oxide, and 0.90 ≤ x ≤ 1.1, preferably 0.95 ≤ x ≤ 1.08, and more preferably 1.0 ≤ x ≤ 1.08.

[0100] The a represents the atomic fraction of nickel among the metal elements excluding lithium in the lithium transition metal oxide, and 0.80 ≤ a < 1.0, preferably 0.80 ≤ a ≤ 0.95, and more preferably 0.85 ≤ a ≤ 0.90. When the nickel content satisfies the above range, high capacity characteristics can be realized.

[0101] The b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, and 0 < b < 0.2, 0 < b ≤ 0.15, or 0.01 ≤ b ≤ 0.10.

[0102] The c represents the atomic fraction of M 1 among the metal elements excluding lithium in the lithium transition metal oxide, and 0 < c < 0.2, 0 < c ≤ 0.15, or 0.01 ≤ c ≤ 0.10.

[0103] The d represents the atomic fraction of M 2represents the atomic fraction, and 0 ≦ d ≦ 0.1 or 0 ≦ d ≦ 0.05 may be satisfied.

[0104] Based on the total weight of the solid matter excluding the solvent in the positive electrode active material slurry, the positive electrode active material may be contained in an amount of 60% to 99% by weight, preferably 70% to 99% by weight, more preferably 80% to 98% by weight.

[0105] The binder is a component that assists in binding the active material, the conductive material, etc. and binding to the current collector.

[0106] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

[0107] Generally, the binder may be contained in an amount of 1% to 20% by weight, preferably 1% to 15% by weight, more preferably 1% to 10% by weight based on the total weight of the solid content excluding the solvent in the positive electrode active material slurry.

[0108] The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1% by weight to 20% by weight based on the total weight of the solid content in the negative electrode slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powder such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powder; conductive powder such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. may be used.

[0109] Generally, the conductive material may be contained in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, more preferably 1% by weight to 10% by weight, based on the total weight of the solids excluding the solvent in the positive electrode mixture slurry.

[0110] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when the positive electrode active material, and optionally a binder and a conductive material, etc. are included. For example, it may be included such that the concentration of the solid content including the positive electrode active material, and optionally a binder and a conductive material, is 50% by weight to 95% by weight, preferably 70% by weight to 95% by weight, more preferably 70% by weight to 90% by weight.

[0111] (2) Negative electrode The negative electrode can be manufactured, for example, by coating a negative electrode mixture slurry containing a negative electrode active material, a binder, a conductive material, and a solvent, etc. on a negative electrode current collector, or a graphite electrode made of carbon (C) or the metal itself can be used as the negative electrode.

[0112] For example, when manufacturing a negative electrode by coating a negative electrode active material slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those with a surface treatment of carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. may be used. Also, similar to the positive electrode current collector, the binding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabric bodies, etc.

[0113] Further, the negative electrode active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0114] The carbon material capable of reversibly intercalating / deintercalating lithium ions is not particularly limited as long as it is a carbon-based negative electrode active material generally used in lithium-ion secondary batteries and can be used without particular limitation. Representative examples thereof include crystalline carbon, amorphous carbon, or both of these may be used. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature fired carbon) or hard carbon, mesophase pitch carbide, fired coke, etc.

[0115] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn, or an alloy of these metals and lithium can be used.

[0116] As the metal composite oxide, PbO, PbO 2 , Pb 2 O 3 , Pb 3 O 4 , Sb 2 O 3 , Sb 2 O 4 , Sb 2 O 5 , GeO, GeO 2 , Bi 2 O 3 , Bi 2 O 4 , Bi 2 O 5 , Li x Fe 2 O 3 (0 ≦ x ≦ 1), Li x WO 2 (0 ≦ x ≦ 1), and Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, elements of Group 1, Group 2, Group 3 of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) selected from the group consisting of can be used.

[0117] As the substance capable of doping and undoping lithium, Si, SiO x (0 < x ≦ 2), Si-Y alloy (wherein Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Si), Sn, SnO 2, Sn-Y (wherein Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Sn), etc. may be mentioned, and at least one of these and SiO 2 may be mixed and used. The element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0118] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadate, etc.

[0119] The additive according to the present invention is particularly effective when Si or SiO x (0 < x ≦ 2) is used as the negative electrode active material. Specifically, when using a Si-based negative electrode active material, if a strong SEI layer is not formed on the surface of the negative electrode during initial activation, the life characteristics will be promoted to decline due to intense volume expansion and contraction during the progress of the cycle. However, the additive according to the present invention can form a strong SEI layer while having elasticity, so that a secondary battery using a Si-based negative electrode active material can have excellent life characteristics and storage characteristics.

[0120] The negative electrode active material may be contained in an amount of 60% by weight to 99% by weight, preferably 70% by weight to 99% by weight, more preferably 80% by weight to 98% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0121] Examples of the binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof. Specifically, styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC) can be used because of its high thickening property.

[0122] Generally, the binder may be contained in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, more preferably 1% by weight to 10% by weight, based on the total weight of the solids excluding the solvent in the negative electrode binder slurry.

[0123] The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1% by weight to 20% by weight based on the total weight of the solid content in the negative electrode binder slurry. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, carbon powder such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powder; conductive powder such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0124] The conductive material may be contained in an amount of 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, more preferably 1% by weight to 10% by weight, based on the total weight of the solids excluding the solvent in the negative electrode binder slurry.

[0125] The solvent may contain water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when the negative electrode active material, and optionally a binder, a conductive material, etc. are included. For example, it may be included such that the concentration of the solid content including the negative electrode active material, and optionally the binder and the conductive material, is 50% to 95% by weight, preferably 70% to 90% by weight.

[0126] When using the metal itself as the negative electrode, it can be manufactured by a method such as physically bonding, rolling, or vapor depositing the metal on the metal thin film itself or the negative electrode current collector. As the vapor deposition method, a method of electrically vapor depositing or chemically vapor depositing (chemical vapor deposition) the metal can be used.

[0127] For example, the metal bonded / rolled / vapor deposited on the metal thin film itself or the negative electrode current collector may include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals.

[0128] (3) Separator Also, as the separator, a conventional porous polymer film that has been used as a separator, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, may be used alone or in a laminated form, or a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used, but it is not limited thereto. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance may be used, and may optionally be used in a single-layer or multi-layer structure.

[0129] Specifically, as the separator included in the electrode assembly of the present invention, an SRS (safety reinforced separator) separator having a coating layer containing a ceramic component or a polymer substance may be used in order to ensure heat resistance or mechanical strength.

[0130] Specifically, the separator included in the electrode assembly of the present invention includes a porous separator substrate and a porous coating layer that is entirely coated on one or both sides of the separator substrate, and the coating layer is composed of inorganic particles selected from metal oxides, metalloid oxides, metal fluorides, metal hydroxides, and combinations thereof, and a binder polymer that connects and fixes the inorganic particles to each other. It may contain a mixture.

[0131] The coating layer contains, as inorganic particles, Al 2 O 3 、SiO 2 、TiO 2 、SnO 2 、CeO 2 、MgO, NiO, CaO, ZnO, ZrO 2 、Y 2 O 3 、SrTiO 3 、BaTiO 3 、Mg(OH) 2 、and MgF 2 It may contain one or more selected from. Here, the inorganic particles can improve the thermal stability of the separator. That is, the inorganic particles can prevent the separator from shrinking at high temperatures. And the binder polymer can fix the inorganic particles and also improve the mechanical stability of the separator.

[0132] The outer shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape, a rectangular shape, a pouch shape, or a coin shape using a can.

[0133] Hereinafter, the present invention will be described in more detail with specific examples. However, the following examples are merely illustrative for understanding the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope of the description and the technical idea, and it goes without saying that such variations and modifications belong to the scope of the appended claims.

[0134] Example Example 1 (Manufacture of non-aqueous electrolyte) LiPF was dissolved in an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 20:70:10 by volume ratio) to a concentration of 1.2 M to produce a non-aqueous solvent. 0.01 g of the compound of the following Chemical Formula 1-1 and 0.01 g of the compound of the following Chemical Formula 2-1 were added to 99.98 g of the non-aqueous solvent to produce a non-aqueous electrolyte. 6

[0135]

Chemical formula

[0136]

Chemical formula

[0137] (Manufacture of lithium secondary battery) The positive electrode active material (LiNi 0.85 Co 0.05 Mn 0.08 Al 0.02 O 2 ), a conductive material (carbon nanotube), and a binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP), which is a solvent, at a weight ratio of 97.74:0.7:1.56 to produce a positive electrode slurry (solid content: 75.5% by weight). The positive electrode slurry was applied to one side of a positive electrode current collector (Al thin film) with a thickness of 15 μm, and dried and roll pressed to produce a positive electrode.

[0138] ​ The negative electrode active material (silicon; Si), the conductive material (carbon black), and the binder (styrene-butadiene rubber (SBR)-carboxymethyl cellulose (CMC)) were added to N-methyl-2-pyrrolidone (NMP), which is a solvent, at a weight ratio of 70:20.3:9.7 to produce a negative electrode slurry (solid content: 26% by weight). The negative electrode slurry was applied to one side of a negative electrode current collector (Cu thin film) with a thickness of 15 μm, and drying and roll press were performed to produce a negative electrode.

[0139] In a dry room, after interposing a polyolefin-based porous separator coated with inorganic particles Al 2 O 3 between the positive electrode and the negative electrode manufactured above, the non-aqueous electrolyte manufactured above was injected to produce a secondary battery.

[0140] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-1 and 0.01 g of the compound of the following Chemical Formula 3-2 were added to 99.98 g of the non-aqueous solvent manufactured in Example 1 to produce a non-aqueous electrolyte.

[0141]

Chemical formula

[0142] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 2-1 were added to 94.99 g of the non-aqueous solvent manufactured in Example 1 to produce a non-aqueous electrolyte.

[0143] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 3-2 were added to 94.99 g of the non-aqueous solvent manufactured in Example 1 to produce a non-aqueous electrolyte.

[0144] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of Chemical Formula 1-1 and 0.01 g of the compound of Chemical Formula 2-1 were added to 89.99 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0145] Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of Chemical Formula 1-1 and 0.01 g of the compound of Chemical Formula 3-2 were added to 89.99 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0146] Example 7 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 2-1 were added to 85 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0147] Example 8 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of Chemical Formula 1-1 and 5 g of the compound of Chemical Formula 3-2 were added to 85 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0148] Example 9 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of the following Chemical Formula 1-2 and 0.01 g of the compound of Chemical Formula 2-1 were added to 99.98 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0149]

Chemical Formula

[0150] Example 10 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of the following Chemical Formula 1-3 and 0.01 g of the compound of Chemical Formula 2-1 were added to 99.98 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0151] [Chemistry]

[0152] Example 11 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-4 and 0.01 g of the compound of Chemical Formula 2-1 were added to 99.98 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0153] [Chemistry]

[0154] Example 12 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-5 and 0.01 g of the compound of Chemical Formula 2-1 were added to 99.98 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0155] [Chemistry]

[0156] Example 13 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-6 and 0.01 g of the compound of Chemical Formula 2-1 were added to 99.98 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0157] [Chemistry]

[0158] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 1-1 was added to 99.99 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0159] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 10 g of the compound of Chemical Formula 1-1 was added to 90 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0160] Comparative Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 2-1 was added to 99.99 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0161] Comparative Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of Chemical Formula 2-1 was added to 95 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0162] Comparative Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 0.01 g of the compound of Chemical Formula 3-2 was added to 99.99 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0163] Comparative Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of Chemical Formula 3-2 was added to 95 g of the non-aqueous solvent produced in Example 1 to produce a non-aqueous electrolyte.

[0164] Experimental Example 1 - Evaluation of high-temperature cycle characteristics The cycle characteristics of each of the secondary batteries manufactured in Examples 1 to 13 and Comparative Examples 1 to 6 were evaluated.

[0165] Specifically, each of the batteries manufactured in Examples 1 to 13 and Comparative Examples 1 to 6 was charged at 45°C under constant current / constant voltage conditions up to 4.2V at a 0.33C rate (0.05C cut off), and discharged at a constant current of 0.33C down to 3.0V. One cycle was defined as such, and after performing 200 cycles of charge and discharge, the capacity retention rate after 200 cycles with respect to the initial capacity after one cycle was measured. Also, the resistance increase rate after 200 cycles with respect to the initial resistance after one cycle was measured. The results are shown in Table 1 below.

[0166]

Table 1

[0167] Experimental Example 2 - Evaluation of high-temperature storage characteristics The high-temperature storage characteristics were evaluated for each of the secondary batteries manufactured in Examples 1 to 13 and Comparative Examples 1 to 6.

[0168] Specifically, each of the secondary batteries of Examples 1 to 13 and Comparative Examples 1 to 6 was fully charged up to 4.2V and then stored at 60°C for 8 weeks.

[0169] Before storage, the capacity of the fully charged secondary battery was measured and set as the capacity of the initial secondary battery.

[0170] After 8 weeks, the capacity of the stored secondary battery was measured, and the capacity decreased during the 8-week storage period was calculated. The percentage ratio of the decreased capacity with respect to the capacity of the initial secondary battery was calculated to derive the capacity retention rate after 8 weeks. Also, the percentage ratio of the increased resistance with respect to the resistance of the initial secondary battery was calculated to derive the resistance increase rate after 8 weeks. The results are shown in Table 2 below.

[0171]

Table 2

[0172] Experimental Example 3 - Evaluation of thermal stability The thermal stability of each of the secondary batteries manufactured in Examples 1 to 13 and Comparative Examples 1 to 6 was evaluated.

[0173] Specifically, after performing an activation (formation) process on the lithium secondary batteries manufactured in the above Examples and Comparative Examples, charging was performed at 25°C under constant current / constant voltage conditions up to 4.2V at a 0.33C rate (0.05C cut off), and the battery was fully charged up to SOC 100%. After the fully charged battery was heated to 140°C at a heating rate of 5°C / min, it was left for 1 hour each, and a hot box evaluation experiment was conducted to check for ignition. When ignition did not occur, it was evaluated as Pass, and when ignition occurred, it was evaluated as Fail. The results are shown in Table 3 below.

[0174]

Table 3

Claims

1. A non-aqueous electrolyte comprising a lithium salt, an organic solvent, a compound of the following Chemical Formula 1 as a first additive, and a compound of the following Chemical Formula 2 or Chemical Formula 3 as a second additive. 【Chemical 1】 In the above Chemical Formula 1, R １ is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine, SO ２ R' and COR', R’ is any one selected from the group consisting of an alkyl group having 1 to 5 carbon atoms which may be substituted with fluorine, an alkenyl group having 2 to 5 carbon atoms which may be substituted with fluorine, and an alkynyl group having 2 to 5 carbon atoms which may be substituted with fluorine. R ２ and R ３ is each independently any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms, [Chemical 2] In the above Chemical Formula 2, R is an alkylene group having 1 to 3 carbon atoms which may be substituted with fluorine. R ４ ~R ６ is each independently any one selected from the group consisting of H, an alkyl group having 1 to 3 carbon atoms, and a nitrile group. [Chemical Formula 3] In the above Chemical Formula 3, R ７ is an alkylene group having 1 to 8 carbon atoms which may be substituted with fluorine, R ８ is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl group having 3 to 8 carbon atoms.

2. The non-aqueous electrolyte according to Claim 1, wherein the compound of Chemical Formula 1 is any one selected from the following Chemical Formulas 1-1 to 1-6. [Chemical Formula 4] [Chemical Formula 5] 【Chemical Formula 6】 【Chemical Formula 7】 【Chemical 8】 【Chemical Formula 9】

3. The non-aqueous electrolyte according to Claim 1, wherein the compound of Chemical Formula 2 is the compound of the following Chemical Formula 2-1. 【Chemical Formula 10】

4. The non-aqueous electrolyte according to Claim 1, wherein the compound of Chemical Formula 3 is the compound of the following Chemical Formula 3-1. 【Chemical Formula 11】 In the above Chemical Formula 3-1, n is a natural number from 1 to 8. R ８ is H, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

5. The non-aqueous electrolyte according to Claim 1, wherein the compound of Chemical Formula 3 is the compound of the following Chemical Formula 3-2. 【Chemical 12】

6. The non-aqueous electrolyte according to Claim 1, wherein the first additive is contained in an amount of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

7. The non-aqueous electrolyte according to Claim 1, wherein the second additive is contained in an amount of 0.01 parts by weight to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

8. The non-aqueous electrolyte according to Claim 1, wherein the first additive and the second additive are contained in a weight ratio of 1:0.001 to 1:

500.

9. The lithium salt is LiCl, LiBr, LiI, LiBF ４ , LiClO ４ , LiB １０ Cl １０ , LiAlCl ４ , LiAlO ２ , LiPF ６ , LiSO ３ CF ３ , LiCO ２ CH ３ , LiCO ２ CF ３ , LiAsF ６ , LiSbF ６ , LiSO ３ CH ３ , LiN(SO ２ F) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , and one or more selected from the group consisting of LiN(SO ２ CF ３ ) ２ ; the non-aqueous electrolyte according to claim 1.

10. The non-aqueous electrolyte according to Claim 1, wherein the lithium salt is contained at a concentration of 0.5 M to 5.0 M.

11. The non-aqueous electrolyte according to Claim 1, wherein the organic solvent contains at least one organic solvent selected from the group consisting of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

12. A lithium secondary battery comprising a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and the non-aqueous electrolyte according to any one of Claims 1 to 11.

13. The lithium secondary battery according to Claim 12, wherein the positive electrode active material layer contains a lithium nickel-based oxide represented by the following Chemical Formula 4 as a positive electrode active material. [Chemical Formula 4] Li ｘ Ni ａ Co ｂ M １ ｃ M ２ ｄ O ２ In the chemical formula 4, M １ is Mn, Al, or a combination thereof, and M ２ is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and 0.90 ≦ x ≦ 1.1, 0.80 ≦ a < 1.0, 0 < b < 0.2, 0 < c < 0.2, 0 ≦ d ≦ 0.

1.

14. The negative electrode active material layer contains SiO as the negative electrode active material ｘ The lithium secondary battery according to claim 12, comprising (0 ≦ x < 2).

Images