Nonaqueous electrolyte and lithium secondary battery comprising same

Abstract

The present invention provides a non-aqueous electrolyte including a lithium salt, an organic solvent, and an additive, in which the additive includes a compound represented by a specific chemical formula. The non-aqueous electrolyte according to the present invention comprises an additive having excellent electrode film protection and O2 removal effects, and thus can simultaneously improve cycle characteristics and resistance characteristics of a lithium secondary battery comprising the non-aqueous electrolyte.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2022-0125850 filed on September 30, 2022, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery comprising the same. Background Art

[0004] In recent years, as the application areas of lithium secondary batteries have rapidly expanded to power supply for electronic equipment such as electrical, electronic, communication, and computers, as well as the storage and supply of electrical energy for large-area equipment such as automobiles and power storage devices, the demand for secondary batteries with high capacity, high output, and high stability has been increasing.

[0005] In particular, in lithium secondary batteries for automobile use, high capacity, high power and long life characteristics have become important. In order to achieve high capacity of lithium secondary batteries, it is conceived to drive the lithium secondary batteries at a high voltage.

[0006] However, when a lithium secondary battery is driven at a high voltage, the film or electrode surface structure formed on the positive / negative electrode surface may deteriorate due to the side reaction caused by the degradation of the electrolyte during battery charging and discharging, so that transition metal ions may be dissolved from the positive electrode surface. As described above, the dissolved transition metal ions are electrodeposited on the negative electrode, which reduces the passivation ability of the solid electrolyte interface (SEI) film of the negative electrode, thereby causing the problem of negative electrode degradation. When the positive electrode potential increases, or when the battery is exposed to high temperature, the degradation phenomenon of the secondary battery tends to accelerate.

[0007] In addition, when a lithium secondary battery is driven at a high voltage, active oxygen dissociates from the positive electrode active material contained in the positive electrode, and the active oxygen causes a side reaction with an organic solvent such as cyclic carbonate in a non-aqueous electrolyte to produce gases such as CO or CO2, which causes the battery durability to continue to decrease. Summary of the invention

[0008] Technical issues

[0009] One aspect of the present invention provides a non-aqueous electrolyte that forms a stable film on a positive electrode / anode, thereby reducing electrolyte side reactions, has an excellent O2 scavenging effect, and can effectively reduce the resistance of a secondary battery.

[0010] Another aspect of the present invention provides a lithium secondary battery having reduced resistance and excellent lifespan performance by including the above-mentioned nonaqueous electrolyte.

[0011] Technical Solution

[0012] According to one aspect of the present invention, there is provided a non-aqueous electrolyte including a lithium salt, an organic solvent and an additive, wherein the additive includes a compound represented by the following Chemical Formula 1.

[0013] [Chemical formula 1]

[0014]

[0015] In the above Chemical Formula 1, R1 is a substituent including a halogen, a nitrile group, a propargyl group, an ether group, a keto group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and R2 is a substituent represented by the following Chemical Formula 2,

[0016] [Chemical formula 2]

[0017]

[0018] In the above Chemical Formula 2, R3 is selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 1 to 10 carbon atoms, * is a bonding site, n is an integer of 0 to 5, m is an integer of 1 to 6, and n+m is an integer of 1 to 6.

[0019] According to another aspect of the present invention, there is provided a lithium secondary battery comprising: a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the above nonaqueous electrolyte.

[0020] Beneficial effects

[0021] The non-aqueous electrolyte of the present invention contains a coumarin compound substituted with a substituent containing an ester group as an additive. The additive can form a film having excellent durability to the positive electrode / negative electrode and reduced resistance, thereby inhibiting the dissolution of transition metals from the positive electrode and inhibiting electrolyte side reactions in the electrode. In addition, since the active oxygen compound generated by the positive electrode is combined with the coumarin structure contained in the compound represented by the above chemical formula 1, the non-aqueous electrolyte of the present invention has the effect of inhibiting electrolyte decomposition and gas generation (O2 scavenging effect).

[0022] Therefore, a lithium secondary battery including the above nonaqueous electrolyte may have improved resistance properties and lifespan properties at the same time. DETAILED DESCRIPTION

[0023] It will be understood that the words or terms used in the specification and claims of the present invention should not be interpreted as limited to the meanings defined in commonly used dictionaries. It will be further understood that based on the inventors can appropriately define the meaning of the words or terms to best explain the principles of the present invention, the words or terms should be interpreted as having a meaning consistent with its meaning in the context of the relevant technology and the technical concept of the present invention.

[0024] In this specification, it should be understood that the terms "comprising", "including" or "having" are intended to specify the presence of stated features, numbers, steps, elements or a combination thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, elements or a combination thereof.

[0025] Meanwhile, before describing the present invention, unless otherwise specified in the present invention, "*" refers to a connecting portion (bonding site) between the same or different atoms or terminal portions of a chemical formula.

[0026] In addition, in this specification, it should be understood that in the description of "a to b carbon atoms" herein, "a" and "b" each refer to the number of carbon atoms contained in a particular functional group. That is, the functional group may contain "a" to "b" carbon atoms. For example, "alkyl having 1 to 5 carbon atoms" refers to a C1-C5 alkyl having 1 to 5 carbon atoms, i.e., CH3-, CH3CH2-, CH3CH2CH2-, (CH3)2CH-, CH3CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2-, CH3CH2CH2CH2CH2-, (CH3)2CHCH2CH2-, etc.

[0027] In addition, in the present specification, an alkyl group, an alkenyl group or an alkynyl group may be substituted or unsubstituted. Unless otherwise defined, the term “substituted” means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, and for example, it means substitution 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 cycloalkynyl 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, a heterocycloalkynyl group having 2 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, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, and a halogenated aryl group having 6 to 20 carbon atoms.

[0028] Hereinafter, the present invention will be described in more detail.

[0029] Non-aqueous electrolytes

[0030] The present invention relates to a non-aqueous electrolyte, and more specifically, the non-aqueous electrolyte may be a non-aqueous electrolyte for a lithium secondary battery.

[0031] The nonaqueous electrolyte of the present invention includes a lithium salt, an organic solvent, and an additive, wherein the additive includes a compound represented by the following Chemical Formula 1.

[0032] [Chemical formula 1]

[0033]

[0034] In the above Chemical Formula 1, R1 is a substituent including a halogen, a nitrile group, a propargyl group, an ether group, a keto group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and R2 is a substituent represented by the following Chemical Formula 2,

[0035] [Chemical formula 2]

[0036]

[0037] In the above Chemical Formula 2, R3 is selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 1 to 10 carbon atoms, * is a bonding site, n is an integer of 0 to 5, m is an integer of 1 to 6, and n+m is an integer of 1 to 6.

[0038] The non-aqueous electrolyte of the present invention comprises a coumarin compound substituted with a substituent containing an ester group as an additive. The additive can form a film having excellent durability and reduced resistance to the positive / negative electrode, thereby inhibiting the dissolution of transition metals from the positive electrode and inhibiting electrolyte side reactions in the electrode. In addition, since the active oxygen compound produced by the positive electrode is combined with the coumarin structure contained in the compound represented by the above chemical formula 1, the non-aqueous electrolyte of the present invention has the effect of inhibiting electrolyte decomposition and gas generation (O2 removal effect). Therefore, the lithium secondary battery comprising the above-mentioned non-aqueous electrolyte can have improved resistance properties and life properties at the same time.

[0039] (1) Lithium salt

[0040] As the lithium salt used in the present invention, various lithium salts commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without limitation. For example, the lithium salt may include Li + As cations, it may contain F-, Cl-, Br - 、I-、NO3 - 、N(CN)2- 、BF4 - 、ClO4 - 、AlO4 - 、AlCl4 - PF6 - 、SbF6 - 、AsF6 - , B 10 Cl 10 - 、BF2C2O4 - , BC4O8 - PF4C2O4 - PF2C4O8 - 、(CF3)2PF4 - 、(CF3)3PF3 - 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - CF3SO3 - 、C4F9SO3 - CF3CF2SO3 - 、(FSO2)2N - CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、CH3SO3 - CF3(CF2)7SO3 - CF3CO2 - 、CH3CO2 - 、SCN - and (CF3CF2SO2)2N - At least one of the group consisting of is used as an anion.

[0041] Specifically, the lithium salt may include a salt selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10, LiB(C2O4)2(LiBOB), LiCF3SO3, LiN(SO2F)2(LiFSI), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiN(SO2CF2CF3)2(LiBETI). Specifically, the lithium salt may include at least one selected from the group consisting of LiBF4, LiClO4, LiPF6, LiB(C2O4)2(LiBOB), LiCF3SO3, LiN(SO2CF3)2(LiTFSI), LiN(SO2F)2(LiFSI) and LiN(SO2CF2CF3)2(LiBETI).

[0042] In the non-aqueous electrolyte, the concentration of the lithium salt included may be 0.5 M to 5 M, specifically 0.8 M to 4 M, and more specifically 0.8 M to 2.0 M. When the concentration of the lithium salt satisfies the above range, Li + The transference number and the degree of dissociation of lithium ions are improved, thereby improving the output properties of the battery.

[0043] (2) Organic solvents

[0044] The organic solvent is a non-aqueous solvent commonly used in lithium secondary batteries, and is not particularly limited as long as it can minimize decomposition caused by oxidation reactions and the like during charging and discharging of the secondary battery.

[0045] Specifically, the organic solvent may include at least one 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.

[0046] Specifically, the organic solvent may include a cyclic carbonate-based solvent, a linear carbonate-based solvent or a mixture thereof.

[0047] The cyclic carbonate organic solvent is a high viscosity organic solvent with a high dielectric constant, so it is easy to dissociate the lithium salt in the electrolyte. Specifically, the cyclic carbonate organic solvent may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and vinylene carbonate, and more specifically, may include ethylene carbonate.

[0048] In addition, the linear carbonate organic solvent is an organic solvent with low viscosity and low dielectric constant. Specifically, the linear carbonate organic solvent may include at least one 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, more specifically, may include ethyl methyl carbonate (EMC).

[0049] The organic solvent may be a mixture of a cyclic carbonate organic solvent and a linear carbonate organic solvent. At this time, the cyclic carbonate organic solvent and the linear carbonate organic solvent may be mixed in a volume ratio of 10:90 to 40:60, specifically, a volume ratio of 10:90 to 30:70, more specifically, a volume ratio of 15:85 to 30:70. When the mixing ratio of the cyclic carbonate solvent and the linear carbonate solvent satisfies the above range, high dielectric constant and low viscosity characteristics can be satisfied simultaneously, and excellent ionic conductivity properties can be achieved.

[0050] In addition, in order to prepare an electrolyte with high ionic conductivity, the organic solvent may include at least one carbonate organic solvent selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents, and may further include at least one ester organic solvent selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0051] The linear ester organic solvent may specifically include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0052] In addition, the cyclic ester organic solvent may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0053] Meanwhile, if necessary, the organic solvent may also use any organic solvent commonly used in non-aqueous electrolytes without limitation, for example, at least one organic solvent selected from ether organic solvents, glycol ether organic solvents and nitrile organic solvents may be further included.

[0054] As the ether solvent, any one selected from the group consisting of dimethyl ether, ethyl 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 thereof can be used, but the present invention is not limited thereto.

[0055] Glycol ether solvents are solvents having a higher dielectric constant and a lower surface tension and lower reactivity with metals than straight-chain carbonate organic solvents, and may include at least one selected from the group consisting of dimethoxyethane (glycol ether, DME), diethoxyethane, diethylene glycol ether, triethylene glycol ether, and tetraethylene glycol ether (TEGDME), but are not limited thereto.

[0056] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, octanonitrile, heptanecarbonitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, benzyl cyanide, 2-fluorophenyl cyanide and 4-fluorophenyl cyanide, but is not limited thereto.

[0057] (3) Additives

[0058] The nonaqueous electrolyte of the present invention includes a compound represented by the following Chemical Formula 1.

[0059] [Chemical formula 1]

[0060]

[0061] In the above Chemical Formula 1, R1 is a substituent including a halogen, a nitrile group, a propargyl group, an ether group, a keto group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and R2 is a substituent represented by the following Chemical Formula 2,

[0062] [Chemical formula 2]

[0063]

[0064] In the above Chemical Formula 2, R3 is selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 1 to 10 carbon atoms, * is a bonding site, n is an integer from 0 to 5, m is an integer from 1 to 6, and n+m is an integer from 1 to 6. Meanwhile, when there are a plurality of R1s in Chemical Formula 1, the plurality of R1s may be the same as or different from each other. In addition, when there are a plurality of R2s in Chemical Formula 1, the plurality of R2s may be the same as or different from each other.

[0065] The compound represented by the above chemical formula 1 is a coumarin compound containing a substituent containing an ester group. The coumarin structure contained in the above chemical formula 1 has a higher reaction energy with active oxygen than organic solvents such as ethylene carbonate, so in the process of generating active oxygen, the coumarin structure combines with active oxygen earlier than the organic solvent. Therefore, when the compound of the above chemical formula 1 is contained in the non-aqueous electrolyte, the active oxygen compound generated by the positive electrode combines with the coumarin structure contained in the compound represented by the above chemical formula 1, thereby showing the effect of inhibiting electrolyte decomposition and gas generation.

[0066] In addition, the compound represented by the above chemical formula 1 can be rapidly reduced and decomposed upon initial activation and form a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode. The coumarin structure contained in the compound represented by the above chemical formula 1 has strong reducibility at the negative electrode, and the ring structure is open at the initial activation of the lithium secondary battery, so that a polyethylene oxide polymer SEI layer can be formed. The polymer SEI layer has the advantages of excellent flexibility and resilience. In addition, the ester-containing substituent (Formula 2) contained in the compound represented by Chemical Formula 1 is preferred in terms of assisting the formation of an SEI film with reduced resistance, helping to improve the lithium ion conductivity due to the oxygen contained therein when forming the SEI film, and promoting the SEI film formation reaction by reducing the electron density of the substituent.

[0067] Therefore, the non-aqueous electrolyte containing the compound of Chemical Formula 1 containing both a coumarin structure and a substituent containing an ester group as an additive can reduce the resistance to the negative electrode and form an SEI film with excellent durability, thereby greatly improving the life performance and resistance properties of the lithium secondary battery containing the non-aqueous electrolyte.

[0068] Specifically, the compound represented by the above Chemical Formula 1 may include at least one selected from the group consisting of compounds represented by the following Chemical Formula 1-A and Chemical Formula 1-B, and more specifically, may include the compound represented by Chemical Formula 1-A.

[0069] [Chemical Formula 1-A]

[0070]

[0071] [Chemical Formula 1-B]

[0072]

[0073] In the above Chemical Formula 1-A and the above Chemical Formula 1-B, R1, R2 and n are as defined in Chemical Formula 1.

[0074] If R2 is substituted on coumarin as in the above chemical formula 1-A and chemical formula 1-B, it is preferred in promoting the SEI film formation reaction of the coumarin structure itself. In particular, if R2 is substituted on coumarin as in the above chemical formula 1-A, the SEI film formation reaction can be further promoted.

[0075] More specifically, the compound represented by the above Chemical Formula 1 may include at least one selected from the group consisting of compounds represented by Chemical Formula 1-a and Chemical Formula 1-b, and even more specifically, may include a compound represented by the following Chemical Formula 1-a.

[0076] [Chemical formula 1-a]

[0077]

[0078] [Chemical formula 1-b]

[0079]

[0080] In the above Chemical Formula 1-a and Chemical Formula 1-b, R2 is as defined in Chemical Formula 1.

[0081] In the above Chemical Formula 2, R3 is selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 1 to 10 carbon atoms, and specifically, may be an alkyl group having 1 to 10 carbon atoms, and more specifically, may be an alkyl group having 1 to 3 carbon atoms.

[0082] In addition, the compound represented by the above Chemical Formula 1 may include at least one selected from the group consisting of compounds represented by the following Chemical Formula 1-a-1, the following Chemical Formula 1-a-2, the following Chemical Formula 1-b-1, and the following Chemical Formula 1-b-2. Specifically, it may include at least one selected from the group consisting of compounds represented by the following Chemical Formula 1-a-1 and the following Chemical Formula 1-a-2. More specifically, it may include the compound represented by the following Chemical Formula 1-a-1.

[0083] [Chemical formula 1-a-1]

[0084]

[0085] [Chemical formula 1-a-2]

[0086]

[0087] [Chemical formula 1-b-1]

[0088]

[0089] [Chemical formula 1-b-2]

[0090]

[0091] The content of the compound represented by the above chemical formula 1 in the non-aqueous electrolyte can be 0.01 wt % to 5 wt %, specifically 0.05 wt % to 4.5 wt %, more specifically 0.2 wt % to 1.5 wt %, and more specifically 0.4 wt % to 0.8 wt %. When the content of the compound represented by the above chemical formula 1 satisfies the above range, it is preferred to fully exert the aforementioned effect of protecting the electrode interface and inhibiting the decomposition of the organic solvent and preventing the side reaction while preventing the increase in resistance of the lithium secondary battery caused by excessive addition and the resulting decrease in life performance.

[0092] The additive may further include a supplementary additive together with the compound of the above Chemical Formula 1. In addition, the supplementary additive may be included in the non-aqueous electrolyte to prevent the non-aqueous electrolyte from decomposing under a high output environment to cause the negative electrode to collapse, or to achieve low-temperature high-rate discharge characteristics, high-temperature stability, prevent overcharging, and suppress battery expansion at high temperatures.

[0093] Specifically, the supplementary additive may be at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, propylene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiPO2F2, lithium difluorooxalatoborate (LiODFB), lithium dioxalatoborate (LiBOB), 3-trimethoxysilylpropyl-N-aniline (TMSPa) and tris(trimethylsilyl)phosphite (TMSPi), more specifically, may be at least one selected from the group consisting of vinylene carbonate and 1,3-propane sultone.

[0094] The supplementary additive may be contained in the non-aqueous electrolyte in an amount of 0.1 wt % to 15 wt %.

[0095] Lithium secondary battery

[0096] In addition, the present invention provides a lithium secondary battery including the above nonaqueous electrolyte.

[0097] Specifically, the lithium secondary battery includes: a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the above-mentioned nonaqueous electrolyte.

[0098] At this time, the lithium secondary battery of the present invention can be manufactured by conventional methods known in the art. For example, the lithium secondary battery of the present invention can be manufactured in the following manner: forming an electrode assembly in which a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode are stacked in sequence, and then inserting the electrode assembly into a battery case, and then injecting the nonaqueous electrolyte of the present invention therein.

[0099] (1) Positive electrode

[0100] The positive electrode contains a positive electrode active material.

[0101] The positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. At this time, the positive electrode active material may be included in the positive electrode active material layer.

[0102] There is no particular limitation on the positive electrode current collector as long as it has high conductivity and does not cause chemical changes in the battery. Specifically, the positive electrode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, fired carbon, and aluminum cadmium alloy, and preferably aluminum.

[0103] The thickness of the positive electrode current collector can generally be 3 μm to 500 μm.

[0104] The positive electrode current collector may have fine irregularities formed on its surface to improve the binding force of the positive electrode active material. For example, the positive electrode current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, and non-woven fabric body.

[0105] The positive electrode active material layer is provided on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer may be provided on one surface or both surfaces of the positive electrode current collector.

[0106] The positive electrode active material layer may contain a positive electrode active material.

[0107] The positive electrode active material is a compound capable of reversibly inserting and extracting lithium, and specifically may include a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of nickel, cobalt, manganese, and aluminum, and preferably a lithium transition metal composite oxide containing lithium and a transition metal including nickel, cobalt, and manganese.

[0108] For example, the lithium transition metal composite oxide may be a lithium manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium cobalt-based oxide (e.g., LiCoO2, etc.), a lithium nickel-based oxide (e.g., LiNiO2, etc.), a lithium nickel manganese-based oxide (e.g., LiNi 1- Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), a lithium nickel cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium manganese cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Coz1 O4 (where 0<Z1<2), etc.), lithium nickel manganese cobalt oxides (such as Li(Ni p Co q Mn r1 )O2 (where 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.) or lithium nickel cobalt transition metal (M) oxide (e.g. Li(Ni p2 Co q2 Mn r3 M s2 )O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, p2, q2, r3 and s2 are each the atomic fractions of independent elements, wherein 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), etc., and may contain any one of them or a compound of two or more thereof. Among these materials, in terms of being able to improve the capacity and stability of the battery, the lithium transition metal composite oxide may be LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2、Li(Ni 0.5 Mn 0.3 Co 0.2 )O2、Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.) or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc. When considering the significant improvement effect of controlling the type and content ratio of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2、Li(Ni 0.5 Mn 0.3 Co 0.2 )O2、Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn0.1 Co 0.1 )O2, etc., any one of them or a mixture of two or more thereof can be used.

[0109] More specifically, the positive electrode active material is a lithium transition metal composite oxide, and may contain more than 60 mol% of nickel relative to the total molar number of transition metals contained in the lithium transition metal composite oxide. Specifically, the positive electrode active material is a lithium transition metal composite oxide, the transition metal includes nickel and at least one selected from manganese, cobalt and aluminum, and the content of nickel relative to the total molar number of transition metals may be more than 60 mol%, specifically 60 mol% to 90 mol%. When a lithium transition metal composite oxide with a high nickel content is used together with the above-mentioned non-aqueous electrolyte, it is preferred in terms of reducing gaseous byproducts generated due to structural collapse.

[0110] In addition, the positive electrode active material may include a lithium transition metal composite oxide represented by the following Chemical Formula 5.

[0111] [Chemical formula 5]

[0112] Li 1+x (Ni a Co b Mn c M d )O2

[0113] In the above chemical formula 5, M is at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, 1+x, a, b, c and d are each the atomic fractions of independent elements, wherein 0≤x≤0.2, 0.50≤a<1, 0 <b≤0.25,0<c≤0.25,0≤d≤0.1,a+b+c+d=1。

[0114] Preferably, a, b, c and d may be 0.70≤a≤0.95, 0.025≤b≤0.20, 0.025≤c≤0.20 and 0≤d≤0.05, respectively.

[0115] Furthermore, a, b, c and d may be 0.80≤a≤0.95, 0.025≤b≤0.15, 0.025≤c≤0.15 and 0≤d≤0.05, respectively.

[0116] Furthermore, a, b, c and d may be 0.85≤a≤0.90, 0.05≤b≤0.10, 0.05≤c≤0.10 and 0≤d≤0.03, respectively.

[0117] Meanwhile, the positive electrode active material may include a perlithiated manganese-rich oxide containing at least 50 mol % of Mn in all metals except lithium and having a molar ratio of lithium to transition metal greater than 1.

[0118] When the perlithium manganese-rich oxide is used as a positive electrode active material, during the initial activation process, active oxygen is generated while the perlithium manganese-rich oxide in the rock salt phase is decomposed. The active oxygen corrodes and decomposes organic solvents such as ethylene carbonate, and produces gas and resistance byproducts, thereby deteriorating the physical properties of the battery. However, in the present invention, since the non-aqueous electrolyte contains a compound that is more reactive with active oxygen than the organic solvent, the active oxygen generated during the initial activation process can first combine with the compound shown in the above chemical formula 1 earlier than the organic solvent, thereby minimizing the side effects caused by the decomposition of the organic solvent.

[0119] The perlithium manganese-rich oxide may be a compound represented by the following chemical formula 6:

[0120] [Chemical formula 6]

[0121] Li 1+s [Ni t Co u Mn v M 1 w ]O 2+z

[0122] In the above chemical formula 6, M 1 It is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo. In addition, in the above chemical formula 6, it can be 0.05≤s≤1, 0≤t≤0.5, 0≤u≤0.3, 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1, preferably 0.05≤s≤1, 0≤t≤0.5, 0≤u≤0.1, 0.5≤v<1.0, 0≤w≤0.2, 0≤z≤1, and more preferably 0.10≤s≤0.50, 0.1≤t≤0.5, 0≤u≤0.1, 0.6≤v<1.0, 0≤w≤0.1, 0≤z≤0.50.

[0123] More specifically, the perlithium manganese-rich oxide may be a compound represented by the following chemical formula 6-1:

[0124] [Chemical formula 6-1]

[0125] X Li2MnO3·(1-X)Li[Ni 1-y-z-w Mn y Co z M 1w ]O2

[0126] In the above chemical formula 6-1, M 1 It is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo. In addition, in the above chemical formula 6-1, it can be 0.1≤X≤0.5, 0.5≤y<1, 0≤z≤0.3, 0≤w≤0.2, preferably 0.2≤X≤0.5, 0.5≤y<1, 0≤z≤0.1, 0≤w≤0.2, and more preferably 0.3≤X≤0.5, 0.6≤y<1, 0≤z≤0.1, 0≤w≤0.2.

[0127] In consideration of showing sufficient capacity of the positive electrode active material, the content of the positive electrode active material in the positive electrode active material layer may be 80 wt % to 99 wt %, preferably 92 wt % to 98.5 wt %.

[0128] The positive electrode active material layer may further include a binder and / or a conductive material together with the above-mentioned positive electrode active material.

[0129] The binder is a component used to assist the combination of active materials and conductive materials, etc. and the combination with the collector. Specifically, the binder may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber and fluororubber, preferably including polyvinylidene fluoride.

[0130] In terms of ensuring sufficient binding force between components such as the positive electrode active material, the content of the binder in the positive electrode active material layer may be 1 wt % to 20 wt %, preferably 1.2 wt % to 10 wt %.

[0131] Conductive materials can be used to assist and improve the conductivity in secondary batteries, as long as they are conductive and do not cause chemical changes, without special restrictions. Specifically, the positive electrode conductive material can include: graphite, such as natural graphite or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbons; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium dioxide; and polyphenylene derivatives, which can preferably contain carbon black in terms of improving conductivity.

[0132] In terms of ensuring sufficient conductivity, the content of the conductive material in the positive electrode active material layer may be 1 wt % to 20 wt %, preferably 1.2 wt % to 10 wt %.

[0133] The thickness of the positive electrode active material layer may be 30 μm to 400 μm, preferably 40 μm to 110 μm.

[0134] The positive electrode may be manufactured by coating a positive electrode collector with a positive electrode slurry including a positive electrode active material and optionally a binder, a conductive material, and a solvent for forming a positive electrode slurry, and then drying and rolling the resultant.

[0135] The positive electrode slurry forming solvent may include an organic solvent, such as N-methyl-2-pyrrolidone (NMP). The positive electrode slurry may have a solid content of 40 wt % to 90 wt %, specifically 50 wt % to 80 wt %.

[0136] (2) Negative electrode

[0137] The negative electrode may be opposite the positive electrode.

[0138] The negative electrode contains a negative electrode active material.

[0139] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. In this case, the negative electrode active material may be contained in the negative electrode active material layer.

[0140] The negative electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. Specifically, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium and silver, and aluminum-cadmium alloys can be used as the negative electrode current collector.

[0141] The thickness of the negative electrode current collector may generally be 3 μm to 500 μm.

[0142] The negative electrode current collector may have fine concavities and convexities formed on its surface to improve the binding force of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric body.

[0143] The negative electrode active material layer is disposed on at least one surface of the negative electrode collector. Specifically, the negative electrode active material layer may be disposed on one surface or both surfaces of the negative electrode collector.

[0144] The negative electrode active material layer may include a negative electrode active material.

[0145] The negative electrode active material is a material that can reversibly embed / de-embed lithium ions, and may include at least one selected from the group consisting of carbon-based active materials, (quasi-)metallic active materials and lithium metal, and specifically may include at least one selected from carbon-based active materials and (quasi-)metallic active materials.

[0146] The carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, graphene, and fiber carbon, and may preferably include at least one selected from the group consisting of artificial graphite and natural graphite.

[0147] In terms of ensuring structural stability during charge and discharge and reducing side reactions with the electrolyte, the average particle size (D 50 ) can be 10 μm to 30 μm, preferably 15 μm to 25 μm.

[0148] Specifically, the (quasi)metallic active material may include at least one quasi-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, V, Ti and Sn; an alloy of lithium and at least one (quasi-)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, V, Ti and Sn; an oxide of at least one (quasi-)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, V, Ti and Sn; lithium titanium oxide (LTO); lithium vanadium oxide, etc.

[0149] More specifically, the (quasi)metal-based active material may include a silicon-based active material.

[0150] The silicon-based active material may include SiO x Since SiO2 does not react with lithium ions and thus cannot store lithium, x is preferably within the above range, and more preferably, the silicon-based active material may be SiO.

[0151] In terms of ensuring structural stability during charge and discharge and reducing side reactions with the electrolyte, the average particle size (D 50 ) can be 1 μm to 30 μm, preferably 2 μm to 15 μm.

[0152] In the negative electrode active material layer, the content of the negative electrode active material may be 60 wt % to 99 wt %, preferably 75 wt % to 95 wt %.

[0153] The negative electrode active material layer may further include a binder and / or a conductive material together with the negative electrode active material.

[0154] At this time, the binder is used to improve the battery performance by improving the adhesion between the negative electrode active material layer and the negative electrode collector, and can include, for example, at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and materials replacing hydrogen with Li, Na or Ca, etc., and can also include various copolymers thereof.

[0155] In the negative electrode active material layer, the content of the binder may be 0.5 wt % to 10 wt %, preferably 1 wt % to 5 wt %.

[0156] There is no particular limitation on the conductive material as long as it has conductivity and does not cause chemical changes in the battery. For example, the following can be used: graphite, such as natural graphite or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; fluorocarbons; metal powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium dioxide; and conductive materials, such as polyphenylene derivatives, etc.

[0157] In the negative electrode active material layer, the content of the conductive material may be 0.5 wt % to 10 wt %, preferably 1 wt % to 5 wt %.

[0158] The thickness of the negative electrode active material layer may be 10 μm to 100 μm, preferably 50 μm to 80 μm.

[0159] The negative electrode may be manufactured by coating at least one surface of a negative electrode collector with a negative electrode slurry including a negative electrode active material, a binder, a conductive material, and / or a solvent for forming a negative electrode slurry, and then drying and rolling the resultant.

[0160] In terms of promoting the dispersion of the negative electrode active material, the binder and / or the conductive material, the negative electrode slurry forming solvent may include, for example, at least one selected from the group consisting of distilled water, N-methyl-2-pyrrolidone (NMP), ethanol, methanol and isopropanol, preferably distilled water. The solid content of the negative electrode slurry may be 30 wt % to 80 wt %, specifically 40 wt % to 70 wt %.

[0161] (3) Diaphragm

[0162] In addition, as a separator, a common porous polymer film commonly used as a separator can be used alone, for example, a porous polymer film made of a polyolefin polymer (such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer), or a laminate thereof can be used. Alternatively, a common porous non-woven fabric can be used, for example, a non-woven fabric made of glass fiber or polyethylene terephthalate fiber with a high melting point, but the present invention is not limited thereto. In addition, a coated separator including a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength, and can be selectively used in a single-layer or multilayer structure.

[0163] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be cylindrical using a can, square, pouch, or coin-shaped.

[0164] Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the following examples are used for merely promoting the illustrative purpose of understanding the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope and spirit of the present invention, and it is apparent that such changes and modifications are within the scope of the appended claims.

[0165] Examples and Comparative Examples

[0166] Example 1

[0167] (Preparation of non-aqueous electrolyte)

[0168] As the organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 30:70 was used.

[0169] LiPF6 as a lithium salt, a compound represented by the following Chemical Formula 1-a-1, and vinylene carbonate and 1,3-propane sultone as supplementary additives were added to an organic solvent to prepare a nonaqueous electrolyte.

[0170] The concentration of LiPF6 contained in the non-aqueous electrolyte was 1.0M.

[0171] The non-aqueous electrolyte contained 0.5 wt % of a compound represented by the following Chemical Formula 1-a-1.

[0172] Furthermore, the nonaqueous electrolyte contained 0.5% by weight each of vinylene carbonate and 1,3-propane sultone.

[0173] [Chemical formula 1-a-1]

[0174]

[0175] (Manufacturing of lithium secondary batteries)

[0176] The positive electrode active material (Li 1.35 [Ni 0.35 Mn 0.65 ]O2, lithium-rich manganese oxide), a conductive material (carbon black) and a binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 96.0:1.5:2.5 to prepare a positive electrode slurry (solid content of 60 wt%). The positive electrode slurry was coated on one surface of a positive electrode collector (Al film) with a thickness of 13.5 μm, and then dried and rolled to manufacture a positive electrode.

[0177] The negative electrode active material (graphite), the conductive material (carbon black) and the binder (styrene-butadiene rubber) were added to distilled water as a solvent at a weight ratio of 97:1:2 to prepare a negative electrode slurry (solid content of 60 wt%). The negative electrode slurry was coated on one surface of a negative electrode collector (Cu film) having a thickness of 6 μm, and then dried and rolled to manufacture a negative electrode.

[0178] In a dry room, a polyethylene porous film separator was inserted between the positive electrode and the negative electrode manufactured as described above, and then the prepared nonaqueous electrolyte was injected therein to manufacture a secondary battery.

[0179] Example 2

[0180] A nonaqueous electrolyte and a secondary battery were manufactured in the same manner as in Example 1, except that 0.3 wt % of the compound represented by Chemical Formula 1-a-1 was added to the nonaqueous electrolyte of Example 1.

[0181] Example 3

[0182] A nonaqueous electrolyte and a secondary battery were manufactured in the same manner as in Example 1, except that 1.0 wt % of the compound represented by Chemical Formula 1-a-1 was added to the nonaqueous electrolyte of Example 1.

[0183] Comparative Example 1

[0184] A nonaqueous electrolyte and a secondary battery were manufactured in the same manner as in Example 1 except that the compound represented by the above Chemical Formula 1-a-1 was not added.

[0185] Comparative Example 2

[0186] A nonaqueous electrolyte and a secondary battery were manufactured in the same manner as in Example 1, except that 0.5 wt % of a compound represented by the following Chemical Formula X was added to the nonaqueous electrolyte instead of the compound represented by the above Chemical Formula 1-a-1.

[0187] [Chemical formula X]

[0188]

[0189] Experimental example

[0190] Experimental Example 1: Evaluation of Cycle Capacity Retention Rate

[0191] The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 manufactured as described above were charged to 4.35 V and 1 / 40 C at 45° C. under CC / CV and 0.33 C conditions using an electrochemical charge and discharge device, and then discharged to 2.0 V under CC and 0.33 C conditions, which was set as one cycle. 150 charge and discharge cycles were performed to measure the capacity retention rate.

[0192] The capacity retention rate was calculated by the following mathematical formula, and the results are shown in Table 1 below.

[0193] Capacity retention rate (%) = {(discharge capacity after 150 cycles / discharge capacity after 1 cycle)} × 100

[0194] Experimental Example 2: Resistance Evaluation

[0195] The lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 manufactured above were charged to 4.35 V and 1 / 40 C at 45° C. under CC / CV and 0.33 C conditions, and then discharged to 2.0 V under CC and 0.33 C conditions, which was set as one cycle, and 150 charge and discharge cycles were performed.

[0196] After one charge and discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charge and discharge device, the SOC was adjusted to SOC 50%, and then a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated by the difference between the voltage before and after the pulse application.

[0197] After 150 charge and discharge cycles, the resistance after 150 cycles was calculated by the same method as described above. The results are shown in Table 1 below.

[0198] [Table 1]

[0199]

[0200] Referring to Table 1, it can be confirmed that the lithium secondary batteries of Examples 1 to 3 using the nonaqueous electrolyte including the compound represented by Chemical Formula 1 simultaneously improve cycle life performance and resistance characteristics compared to the lithium secondary batteries of Comparative Examples 1 and 2.

[0201] Experimental Example 3: Evaluation of Metal Dissolution

[0202] The secondary batteries of Example 1, Comparative Example 1 and Comparative Example 2 were charged to 4.35 V and 1 / 40 C at 45° C. under CC / CV and 0.33 C conditions, and then discharged to 2.0 V under CC and 0.33 C conditions as one cycle, and 150 charge and discharge cycles were performed.

[0203] Afterwards, the concentration of all metals dissolved in the electrolyte was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES). The metal amounts measured using ICP analysis are shown in Table 2 below.

[0204] [Table 2]

[0205]

[0206] With reference to Table 2, it can be confirmed that the secondary battery using the non-aqueous electrolyte of Example 1 significantly reduces the amount of metal elution during the cyclic charge and discharge process, compared with the secondary batteries of Comparative Examples 1 and 2.

Claims

1. A non-aqueous electrolyte comprising: Lithium salts; organic solvents; and additive, in, The additive comprises a compound represented by the following Chemical Formula 1: [Chemical formula 1] Wherein, in the above chemical formula 1, R1 is a substituent, including a halogen, a nitrile group, a propargyl group, an ether group, a keto group, a carboxyl group, an alkyl group with or without a substituent, an alkenyl group with or without a substituent, an alkynyl group with or without a substituent, an alkoxy group with or without a substituent, a boron group, a borate group, an isocyanate group, an isothiocyanate group, a silyl group, a siloxane group, a sulfone group, a sulfonate group, a sulfate group, or a combination of two or more thereof, and R2 is a substituent represented by the following chemical formula 2, [Chemical formula 2] Wherein, in the above chemical formula 2, R3 is selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 1 to 10 carbon atoms, * is a bonding site, n is an integer of 0 to 5, m is an integer of 1 to 6, and n+m is an integer of 1 to 6.

2. The nonaqueous electrolyte according to claim 1, wherein The compound represented by the above Chemical Formula 1 includes at least one selected from the group consisting of the compound represented by Chemical Formula 1-A and the compound represented by Chemical Formula 1-B: [Chemical Formula 1-A] [Chemical Formula 1-B] In the above Chemical Formula 1-A and the above Chemical Formula 1-B, R1, R2 and n are as defined in Chemical Formula 1.

3. The nonaqueous electrolyte according to claim 1, wherein The compound represented by the above Chemical Formula 1 includes at least one selected from the group consisting of the compound represented by Chemical Formula 1-a and the compound represented by Chemical Formula 1-b: [Chemical formula 1-a] [Chemical formula 1-b] In the above Chemical Formula 1-a and Chemical Formula 1-b, R2 is as defined in Chemical Formula 1.

4. The nonaqueous electrolyte according to claim 1, wherein The compound represented by the above Chemical Formula 1 includes at least one selected from the group consisting of a compound represented by the following Chemical Formula 1-a-1, a compound represented by the following Chemical Formula 1-a-2, a compound represented by the following Chemical Formula 1-b-1, and a compound represented by the following Chemical Formula 1-b-2: [Chemical formula 1-a-1] [Chemical formula 1-a-2] [Chemical formula 1-b-1] [Chemical formula 1-b-2] 5. The nonaqueous electrolyte according to claim 1, wherein The compound represented by the above Chemical Formula 1 may be contained in the non-aqueous electrolyte in an amount of 0.01 wt % to 10 wt %.

6. The nonaqueous electrolyte according to claim 1, wherein The lithium salt includes a salt selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiAlO4, LiAlCl4, LiPF6, LiSbF6, LiAsF6, LiB 10 Cl 10 , LiB(C2O4)2(LiBOB), LiCF3SO3, LiN(SO2F)2(LiFSI), LiCH3SO3, LiCF3CO2, LiCH3CO2 and LiN(SO2CF2CF3)2(LiBETI).

7. The nonaqueous electrolyte according to claim 1, wherein The lithium salt is included in the non-aqueous electrolyte at a molar concentration of 0.5M to 5.0M.

8. The nonaqueous electrolyte according to claim 1, wherein The organic solvent includes at least one selected from the group consisting of a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent.

9. The nonaqueous electrolyte according to claim 1, wherein The additive further comprises at least one supplementary additive selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, propane sultone, propylene sultone, succinonitrile, adiponitrile, ethylene sulfate, LiPO2F2, lithium difluorooxalatoborate (LiODFB), lithium dioxalatoborate (LiBOB), 3-trimethoxysilylpropyl-N-aniline (TMSPa) and tris(trimethylsilyl)phosphite (TMSPi).

10. A lithium secondary battery comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; and The nonaqueous electrolyte according to claim 1.

11. The lithium secondary battery according to claim 10, wherein: The positive electrode active material comprises a perlithiated manganese-rich oxide containing at least 50 mol % of Mn in all metals except lithium and having a molar ratio of lithium to transition metal greater than 1.

12. The lithium secondary battery according to claim 11, wherein The perlithium manganese-rich oxide is a compound represented by the following chemical formula 6: [Chemical formula 6] Li 1+s [Ni t Co u Mr v M 1 w ]O 2+z In the above chemical formula 6, M 1 It is one or more selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, and 0.05≤s≤1, 0≤t≤0.5, 0≤u≤0.3, 0.5≤v<1.0, 0≤w≤0.2, and 0≤z≤1.

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