Nonaqueous electrolyte containing additive for nonaqueous electrolyte and lithium secondary battery containing the same

Abstract

The present invention provides a non-aqueous electrolyte containing an additive for a non-aqueous electrolyte represented by the following chemical formula 1: JPEG2024517276000032.jpg37170In the above chemical formula 1, R1 and R2 are each independently selected from the group consisting of H, F, a nitrile group, a thiocyanate group, an isothiocyanate group, an isocyanate group, an alkoxycarbonyl group having 1 to 10 carbon atoms, an alkylcarbonyl group having 1 to 10 carbon atoms, a sulfonyl group substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms, R3 to R6 are each independently any one selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms (excluding the case where R1 and R2 are simultaneously H).

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0155935, filed on November 12, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a non-aqueous electrolyte containing an additive for a non-aqueous electrolyte and a lithium secondary battery containing the same. [Background technology]

[0003] In recent years, the application areas of lithium secondary batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, communication, and computer equipment to power storage and supply for large-area devices such as automobiles and power storage devices. Accordingly, there has been an increasing demand for high-capacity, high-power, and highly stable secondary batteries.

[0004] In particular, high capacity, high power output, and long life are important characteristics for lithium secondary batteries for automotive applications. To achieve high capacity, secondary batteries often use positive electrode active materials with high nickel content, which have high energy density but low stability, or are operated at high voltages.

[0005] However, when a secondary battery is operated under the above conditions, as charging and discharging proceeds, the coating formed on the surface of the positive and negative electrodes or the electrode surface structure deteriorates due to side reactions caused by electrolyte degradation, which can lead to the elution of transition metal ions from the surface of the positive electrode.The eluted transition metal ions are then electro-deposited on the negative electrode, reducing the passivation ability of the SEI, resulting in the degradation of the negative electrode.

[0006] Such deterioration of secondary batteries tends to be accelerated when the potential of the positive electrode increases or when the battery is exposed to high temperatures.

[0007] Furthermore, when a lithium-ion battery is used continuously for a long time or left at high temperatures, gas is generated and the battery thickness increases, which is known as swelling. It is known that the amount of gas generated at this time depends on the state of the SEI.

[0008] Therefore, in order to solve these problems, research and development efforts are being conducted to find 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 secondary batteries, and improve their stability at high temperatures. Summary of the Invention [Problem to be solved by the invention]

[0009] As a result of extensive research into solving the above problems, an object of the present invention is to provide an additive for a non-aqueous electrolyte that can suppress deterioration of a positive electrode, reduce side reactions between a positive electrode and an electrolyte, and form a stable SEI film on a negative electrode.

[0010] Another object of the present invention is to provide a non-aqueous electrolyte that contains the additive for a non-aqueous electrolyte and thereby has improved stability at high temperatures.

[0011] Another object of the present invention is to provide a lithium secondary battery containing the non-aqueous electrolyte, which has improved high-temperature cycle characteristics and high-temperature storage characteristics, and thus improved performance. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides a non-aqueous electrolyte containing an additive for a non-aqueous electrolyte represented by the following chemical formula 1.

[0013] [Chemical formula 1] [ka]

[0014] In the above Chemical Formula 1, R1 and R2 are each independently H; F; a nitrile group; a thiocyanate group; an isothiocyanate group; an isocyanate group; an alkoxycarbonyl group having 1 to 10 carbon atoms; an alkylcarbonyl group having 1 to 10 carbon atoms; a sulfonyl group substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms; or an oxysulfonyl group substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. CF3; OCF3; COOCF3; and SO2CF3 (excluding the case where R1 and R2 are simultaneously H), and R3 to R6 may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms.

[0015] The present invention also provides a lithium secondary battery containing the non-aqueous electrolyte. [Effects of the Invention]

[0016] The compound represented by Chemical Formula 1, which is provided as an additive for a non-aqueous electrolyte according to the present invention, has a chromone structure. Compounds with a chromone structure preferentially react with superoxide, which is generated by structural collapse of the positive electrode active material at high voltage, and can suppress decomposition of the electrolyte.

[0017] In particular, chromone has a characteristic that the electron density is biased toward oxygen, which has high electron affinity, and therefore the reactivity of the 2nd and 3rd positions, which have relatively low electron density, is high. The compound of the present invention represented by Chemical Formula 1 has electron withdrawing groups substituted at the 2nd and 3rd positions of chromone, which increases the reactivity with superoxide and allows for effective removal of superoxide.

[0018] In addition, the compound represented by Chemical Formula 1 of the present invention can form a coating on the electrode to protect the positive and negative electrodes, and can form an organic coating to reduce battery resistance. That is, the compound represented by Chemical Formula 1 of the present invention can minimize an increase in resistance of a lithium secondary battery and form a stable SEI (Solid Electrolyte Interphase) coating on the surface of the negative electrode. Therefore, it is possible to suppress the decrease in passivation ability of the SEI at high temperatures and prevent deterioration of the negative electrode, thereby improving the battery life characteristics.

[0019] That is, by using the nonaqueous electrolyte of the present invention containing the compound of Chemical Formula 1, an electrode-electrolyte interface that is stable even at high temperatures and has low resistance can be formed, thereby improving the high-temperature cycle characteristics and high-temperature storage characteristics, and realizing a lithium secondary battery with improved performance. DETAILED DESCRIPTION OF THE INVENTION

[0020] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0021] As used herein, the terms "comprises," "comprises," or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the presence or possible addition of one or more other features, numbers, steps, components, or combinations thereof.

[0022] In addition, in the description of "number of carbon atoms a to b" herein, "a" and "b" refer to 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" refers to an alkylene group containing 1 to 5 carbon atoms, i.e., -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH(CH3)CH2-, and -CH(CH3)CH2CH2-.

[0023] In addition, in this specification, the term "alkylene group" means a branched or unbranched divalent hydrocarbon group.

[0024] Furthermore, in this specification, both the alkyl group and the alkylene group may be substituted or unsubstituted. Unless otherwise defined, the term "substituted" means that at least one hydrogen atom bonded to a carbon atom is substituted with an element other than hydrogen, such as 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, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, or a haloaryl group having 6 to 20 carbon atoms.

[0025] The present invention will now be described in more detail.

[0026] non-aqueous electrolyte A non-aqueous electrolyte according to one embodiment of the present invention contains, as an additive, a compound represented by the following Chemical Formula 1. Due to its zwitterionic form, a secondary battery containing the non-aqueous electrolyte of the present invention can have high lithium ion conductivity, suppress deterioration due to interfacial reactions at high temperatures, and have excellent high-temperature cycle characteristics and high-temperature storage characteristics.

[0027] [Chemical formula 1] [ka]

[0028] The compound of Formula 1 has a basic structure of chromone. The chromone-based compound reacts preferentially with superoxide, which is generated by structural collapse of the positive electrode active material at high voltage, and can suppress decomposition of the electrolyte.

[0029] In particular, chromone has a characteristic that the electron density is biased toward oxygen, which has high electron affinity, and therefore the reactivity of the 2nd and 3rd positions, which have relatively low electron density, is high. The compound of the present invention represented by Chemical Formula 1 has electron withdrawing groups substituted at the 2nd and 3rd positions of chromone, which increases the reactivity with superoxide and allows for effective removal of superoxide.

[0030] In addition, the compound represented by Chemical Formula 1 of the present invention can form a coating on the electrode to protect the positive and negative electrodes, and can form an organic coating to reduce battery resistance. That is, the compound represented by Chemical Formula 1 of the present invention can minimize an increase in resistance of a lithium secondary battery and form a stable SEI (Solid Electrolyte Interphase) coating on the surface of the negative electrode. Therefore, it is possible to suppress the decrease in passivation ability of the SEI at high temperatures and prevent deterioration of the negative electrode, thereby improving the battery life characteristics.

[0031] In Chemical Formula 1, R1 and R2 may be electron withdrawing groups. In Chemical Formula 1, R1 and R2 may each independently be any one selected from the group consisting of H; F; a nitrile group; a thiocyanate group; an isothiocyanate group; an isocyanate group; an alkoxycarbonyl group having 1 to 10 carbon atoms; an alkylcarbonyl group having 1 to 10 carbon atoms; a sulfonyl group substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms; an oxysulfonyl group substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms; CF3; OCF3; COOCF3; and SO2CF3. This does not include the case where R1 and R2 are both H. Specifically, the alkoxycarbonyl group having 1 to 10 carbon atoms means -COOR (wherein R is an alkyl group having 1 to 10 carbon atoms). The alkylcarbonyl group having 1 to 10 carbon atoms means -COR' (wherein R' is an alkyl group having 1 to 10 carbon atoms). The sulfonyl group substituted with an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms means -SOR'' (wherein R'' is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms). The oxysulfonyl group substituted with the alkyl group having 1 to 10 carbon atoms, the alkenyl group having 2 to 10 carbon atoms, or the alkynyl group having 2 to 10 carbon atoms means -OSOR''' (wherein R''' is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms).

[0032] In the above Chemical Formula 1, R3 to R6 may each independently represent any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms. In addition, in the above Chemical Formula 1, R3 to R6 may each independently represent any one selected from the group consisting of H and an alkyl group having 1 to 10 carbon atoms.

[0033] Preferably, the compound of Chemical Formula 1 may be a compound represented by the following Chemical Formula 1-1.

[0034] [Chemical formula 1-1] [ka]

[0035] In the above chemical formula 1-1, R1 and R2 may each independently be any one selected from the group consisting of H, F, Cl, an alkoxycarbonyl group having 1 to 10 carbon atoms, and a nitrile group, excluding the case where R1 and R2 are both H.

[0036] The additive for a non-aqueous electrolyte according to the present invention may be any one selected from the group consisting of the following chemical formulas 1-2a to 1-2h.

[0037] [Chemical formula 1-2a] [ka]

[0038] [Formula 1-2b] [ka]

[0039] [Chemical formula 1-2c] [ka]

[0040] [Chemical formula 1-2d] [ka]

[0041] [Chemical formula 1-2e] [ka]

[0042] [Chemical formula 1-2f] [ka]

[0043] [Chemical formula 1-2g] [ka]

[0044] [Chemical formula 1-2h] [ka]

[0045] The additive for a non-aqueous electrolyte according to the present invention may be contained in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 0.5 to 1 part by weight, per 100 parts by weight of the non-aqueous electrolyte. When the content of the compound represented by Chemical Formula 1 satisfies the above range, a sufficient coating film is formed on the positive electrode, which inhibits the elution of transition metals from the positive electrode active material, and the viscosity of the electrolyte is maintained at an appropriate level, resulting in excellent rate characteristics and life characteristics during high-temperature storage.

[0046] The non-aqueous electrolyte according to the present invention may further contain a lithium salt, an organic solvent, or other electrolyte additives.

[0047] The lithium salt is used as an electrolyte salt in a lithium secondary battery and is used as a medium for transferring ions. Generally, the lithium salt contains, for example, Li as a cation. + and as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - , and SCN - At least one selected from the group consisting of:

[0048] Specifically, the lithium salts include LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl10 , LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO2CF2CF3)2 (lithium bis(perfluoroethanesulfonyl)imide; LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide; LiTFSI). In addition to these, any lithium salt commonly used in the electrolyte of a lithium secondary battery can be used without any limitation.

[0049] The lithium salt can be varied as appropriate within a range that is normally usable, but to obtain the optimum effect of forming a corrosion-preventing coating on the electrode surface, it may be contained in the electrolyte at a concentration of 0.5 M to 2.0 M, preferably 0.5 M to 1.8 M, and more preferably 0.7 M to 1.6 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics of the lithium secondary battery during high-temperature storage is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate, allowing for improved electrolyte impregnation.

[0050] The non-aqueous organic solvent may include at least one organic solvent selected from the group consisting of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0051] Specifically, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixed organic solvent thereof.

[0052] The cyclic carbonate organic solvent is a highly viscous organic solvent that has a high dielectric constant and therefore easily dissociates the lithium salt in the electrolyte. Specific examples of the cyclic carbonate organic solvent 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 among these, ethylene carbonate may be included.

[0053] The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, and typical examples thereof include at least one organic solvent 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, and specifically, ethyl methyl carbonate (EMC) may be used.

[0054] In addition, in order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one or more ester organic solvents selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents in addition to at least one or more carbonate organic solvents selected from the group consisting of cyclic carbonate organic solvents and linear carbonate organic solvents.

[0055] Specific examples of such linear ester-based organic solvents include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0056] The cyclic ester organic solvent may be at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0057] Meanwhile, the organic solvent may further include, as needed, any organic solvent commonly used in non-aqueous electrolytes, for example, at least one of an ether-based organic solvent, a glyme-based organic solvent, and a nitrile-based organic solvent.

[0058] The ether solvent may be 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, but is not limited thereto.

[0059] The glyme-based solvent has a higher dielectric constant and lower surface tension than linear carbonate-based organic solvents and is less reactive with metals, and may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME), but is not limited thereto.

[0060] The nitrile 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, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0061] In addition, the non-aqueous electrolyte of the present invention may further contain a known electrolyte additive, as needed, to prevent the non-aqueous electrolyte from being decomposed in a high-power environment, thereby causing the collapse of the negative electrode, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and the effect of suppressing battery expansion at high temperatures.

[0062] Representative examples of such other electrolyte additives may include at least one SEI film-forming additive selected from the group consisting of cyclic carbonate-based compounds, halogen-substituted carbonate-based compounds, sultone-based compounds, sulfate-based compounds, phosphate-based compounds, borate-based compounds, nitrile-based compounds, benzene-based compounds, amine-based compounds, silane-based compounds, and lithium salt-based compounds.

[0063] Examples of the cyclic carbonate compounds include vinylene carbonate (VC) and vinylethylene carbonate.

[0064] The halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0065] The sultone compound includes at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone.

[0066] Examples of the sulfate-based compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0067] The phosphate-based compound may be one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyltrimethylsilylphosphate, trimethylsilylphosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphite.

[0068] Examples of the borate-based compounds include tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), and lithium bisoxalateborate (LiB(C2O4)2, LiBOB).

[0069] 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.

[0070] The benzene-based compound may be fluorobenzene, the amine-based compound may be triethanolamine or ethylenediamine, and the silane-based compound may be tetravinylsilane.

[0071] The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples thereof include lithium difluorophosphate (LiDFP), LiPO2F2, and LiBF4.

[0072] Among these other electrolyte additives, a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), ethylene sulfate (ESA), and lithium difluorophosphate (LiDFP) can form a stronger SEI film on the surface of the negative electrode during the initial activation process of the secondary battery, suppress the generation of gas that may be generated by decomposition of the electrolyte at high temperatures, and improve the high-temperature stability of the secondary battery.

[0073] On the other hand, the other electrolyte additives may be used in combination of two or more kinds, and may be contained in an amount of 0.01 to 30 wt %, specifically 0.1 to 25 wt %, and preferably 1 to 20 wt %, based on the total weight of the non-aqueous electrolyte. When the content of the other electrolyte additives satisfies the above range, better ionic conductivity and improved cycle characteristics can be obtained.

[0074] Lithium secondary battery The present invention also provides a lithium secondary battery containing the non-aqueous electrolyte.

[0075] 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 non-aqueous electrolyte.

[0076] The lithium secondary battery of the present invention can be manufactured by a conventional method known in the art, for example, by forming an electrode assembly in which a positive electrode, a negative electrode, and a separator are sequentially stacked between the positive electrode and the negative electrode, inserting the electrode assembly into a battery case, and injecting the nonaqueous electrolyte according to the present invention into the battery case.

[0077] (1) Positive electrode The positive electrode may be prepared by coating a positive electrode mixture slurry containing a positive electrode active material, a binder, a conductive material, and a solvent on a positive electrode current collector.

[0078] 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 with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel may be used.

[0079] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specifically, it 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 (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 Co z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mnr2 M s2 )O2 (where 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. may be mentioned, and any one or two or more of these compounds may be included.

[0080] Among them, from the point of view of being able to enhance the capacity characteristics and stability of the battery, the lithium metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, 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 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), etc. may be used, and any one or two or more of these mixtures may be used.

[0081] Among them, from the point of view of being able to enhance the capacity characteristics of the battery the most, a positive electrode active material with 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 2.

[0082] [Chemical Formula 2] Li x Ni a Co b M 1 c M 2d O2

[0083] In the above Chemical Formula 2, the M 1 is one or more selected from Mn and Al, and may be preferably Mn or a combination of Mn and Al.

[0084] M 2 may be one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S.

[0085] The x represents the atomic fraction of lithium in the lithium transition metal oxide, and may be 0.90≦x≦1.1, preferably 0.95≦x≦1.08, and more preferably 1.0≦x≦1.08.

[0086] The a represents the atomic fraction of nickel among the metal elements excluding lithium in the lithium transition metal oxide, and may be 0.80≦a<1.0, preferably 0.80≦a≦0.95, and more preferably 0.80≦a≦0.90. When the nickel content satisfies the above range, high capacity characteristics can be achieved.

[0087] The b represents the atomic fraction of cobalt among the metal elements excluding lithium in the lithium transition metal oxide, and is 0. <b<0.2、0<b≦0.15、または0.01≦b≦0.10であってもよい。

[0088] The c is M among the metal elements other than lithium in the lithium transition metal oxide. 1 represents the atomic fraction of 0 <c<0.2、0<c≦0.15、または0.01≦c≦0.10であってもよい。

[0089] The d is the number of metal elements other than lithium in the lithium transition metal oxide. 2 and may be 0≦d≦0.1, or 0≦d≦0.05.

[0090] The positive electrode active material may be contained in an amount of 60 to 99 wt %, preferably 70 to 99 wt %, and more preferably 80 to 98 wt %, based on the total weight of solids in the positive electrode mixture slurry excluding the solvent.

[0091] The binder is a component that assists in binding the active material and the conductive material and in binding them to the current collector.

[0092] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

[0093] Generally, the binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of solids in the positive electrode mixture slurry excluding the solvent.

[0094] The conductive material is a component for further improving the conductivity of the positive electrode active material and may be added in an amount of 1 to 20 wt % based on the total weight of the solid content in the positive electrode mixture slurry. Such a conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystalline structures; conductive fibers such as carbon fiber and metal fiber; conductive powders such as carbon fluoride powder, 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.

[0095] Generally, the conductive material may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of solids in the positive electrode mixture slurry excluding the solvent.

[0096] The solvent may contain an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when containing the positive electrode active material, and optionally a binder, a conductive material, etc. For example, the solvent may be contained so that the concentration of the solids including the positive electrode active material, and optionally a binder and a conductive material, is 50 to 95 wt %, preferably 70 to 95 wt %, and more preferably 70 to 90 wt %.

[0097] (2) Negative electrode The negative electrode can be prepared by coating a negative electrode mixture slurry containing a negative electrode active material, a binder, a conductive material, and a solvent on a negative electrode current collector, or a graphite electrode made of carbon (C) or a metal itself can be used as the negative electrode.

[0098] For example, when a negative electrode is manufactured by coating a negative electrode mixture slurry onto the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, aluminum-cadmium alloy, etc. may be used. Furthermore, as with the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and the negative electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0099] Further, the negative electrode active material may contain 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 with lithium, a metal composite oxide, a material capable of doping and undoping lithium, and a transition metal oxide.

[0100] The carbon material capable of reversibly intercalating / deintercalating lithium ions can be used without particular limitation as long as it is a carbon-based negative electrode active material generally used in lithium ion secondary batteries. 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, and the like.

[0101] As the metal or an alloy of these metals with 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 with lithium can be used.

[0102] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (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) can be used.

[0103] Examples of substances capable of doping and undoping lithium include Si, SiO x (0 < x ≦ 2), Si-Y alloys (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. Further, at least one of these may be mixed with SiO2 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.

[0104] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0105] The negative electrode active material may be contained at 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0106] The binder is a component that aids in the bonding between the conductive material, the active material, and the current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, etc.

[0107] Generally, the binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 10% by weight, based on the total weight of solids in the negative electrode mixture slurry excluding the solvent.

[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 to 20 wt % based on the total weight of the solid content in the negative electrode mixture slurry. Such a conductive material is not particularly limited as long as it does not cause chemical changes in the battery and has conductivity, and examples thereof include carbon powders such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystalline structures; conductive fibers such as carbon fiber and metal fiber; conductive powders such as carbon fluoride powder, 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.

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

[0110] The solvent may include 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 containing the negative electrode active material, and optionally a binder and a conductive material, etc. For example, the solvent may be included so that the concentration of the solids including the negative electrode active material, and optionally a binder and a conductive material, is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

[0111] When a metal is used as the anode, the anode can be fabricated by physically bonding, rolling, or depositing a metal on a metal thin film or the anode current collector. The deposition method can be electrochemical deposition or chemical vapor deposition.

[0112] For example, the metal thin film itself or the metal bonded / rolled / deposited on the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In).

[0113] (3) Separator The separator may be a conventional porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homocopolymer, a propylene homocopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in a laminate, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of a high-melting point glass fiber or polyethylene terephthalate fiber, but is not limited to these. Furthermore, to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may be selectively used as a single-layer or multi-layer structure.

[0114] The external shape of the lithium secondary battery of the present invention is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, or the like.

[0115] The present invention will be described in more detail below with reference to 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 will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the present description and technical concept, and it goes without saying that such changes and modifications fall within the scope of the appended claims.

[0116] Example Example 1 (Production of non-aqueous electrolyte) A non-aqueous solvent was prepared by dissolving LiPF6 at 1.0M and vinylene carbonate (VC) at 0.5% by weight in an organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 3:7 volume ratio), and adding 99.9 g of the non-aqueous solvent to a solution of the compound having the following chemical formula: 1-2a A non-aqueous electrolyte was prepared by adding 0.1 g of the compound.

[0117] [Chemical formula 1-2a] [ka]

[0118] (Lithium secondary battery manufacturing) Cathode active material (LiNi 0.8 Co 0.1 Mn 0.1 A cathode slurry (solid content 75 wt%) was prepared by adding O2, a conductive material (carbon nanotubes), and a binder (polyvinylidene fluoride) in a weight ratio of 50:0.5:0.7 to a solvent, N-methyl-2-pyrrolidone (NMP). The cathode slurry was applied to one side of a 15 μm-thick cathode current collector (Al thin film), dried, and roll-pressed to prepare a cathode.

[0119] Anode active material (graphite), conductive material (carbon nanotubes), and binder (SBR / CMC mixed at a weight ratio of 3 / 1) were added to the solvent HO in a weight ratio of 20:0.1:1 to prepare anode slurry (solid content 50 wt%). The anode slurry was applied to one side of an 8 μm-thick anode current collector (Cu thin film), dried, and roll-pressed to prepare anode.

[0120] A polyethylene separator was interposed between the positive electrode and negative electrode prepared above in a dry room, and then the non-aqueous electrolyte prepared above was poured into the separator to prepare a secondary battery.

[0121] Example 2 A secondary battery was fabricated in the same manner as in Example 1, except that 1.0 g of the compound of Formula 1-2a was added to 99.0 g of the non-aqueous solvent prepared in Example 1 to prepare a non-aqueous electrolyte.

[0122] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 2.0 g of the compound of the following Formula 1-2b was added to 98.0 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0123] [Formula 1-2b] [ka]

[0124] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.5 g of a compound represented by the following Chemical Formula 1-2c to 99.5 g of the non-aqueous solvent prepared in Example 1, instead of the compound represented by Chemical Formula 1-2a.

[0125] [Chemical formula 1-2c] [ka]

[0126] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.5 g of a compound represented by the following Chemical Formula 1-2d to 99.5 g of the non-aqueous solvent prepared in Example 1, instead of the compound represented by Chemical Formula 1-2a.

[0127] [Chemical formula 1-2d] [ka]

[0128] Example 6 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.5 g of a compound represented by the following Chemical Formula 1-2h to 99.5 g of the non-aqueous solvent prepared in Example 1, instead of the compound represented by Chemical Formula 1-2a.

[0129] [Chemical formula 1-2h] [ka]

[0130] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was prepared using 100 g of the non-aqueous solvent prepared in Example 1.

[0131] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.5 g of the compound of the following Chemical Formula A, instead of the compound of Chemical Formula 1-2a, to 99.5 g of the non-aqueous solvent prepared in Example 1.

[0132] [Chemical formula A] [ka]

[0133] Comparative Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by adding 0.5 g of the compound represented by the following chemical formula B, instead of the compound represented by the chemical formula 1-2a, to 99.5 g of the non-aqueous solvent prepared in Example 1.

[0134] [Chemical formula B] [ka]

[0135] Experimental Example 1: Evaluation of high-temperature cycle characteristics The cycle characteristics of each of the secondary batteries produced in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated.

[0136] Specifically, each of the batteries manufactured in Examples 1 to 6 and Comparative Examples 1 to 3 was charged at 45° C. at a constant current of 0.33 C to 4.2 V, then charged at a constant voltage to 1 / 40 C, and discharged at a constant current of 0.33 C to 2.5 V, counting as one cycle. After 100 charge-discharge cycles, the resistance increase rate relative to the initial resistance after 100 cycles was measured. The results are shown in Table 1 below.

[0137] [Table 1]

[0138] As shown in Table 1, Examples 1 to 6, which used the nonaqueous electrolyte additive of the present invention, had a lower resistance increase rate and better life characteristics than Comparative Example 1, which did not use the additive. Furthermore, Examples 1 to 6, which used the nonaqueous electrolyte additive of the present invention, in which electron-withdrawing groups are substituted at the 2- and 3-positions of chromone, had a lower resistance increase rate and better life characteristics than Comparative Example 2, which used an additive of Formula A without substituents at the 2- and 3-positions of chromone, and Comparative Example 3, which used an additive of Formula B in which electron-donating groups are substituted at the 2- and 3-positions of chromone.

[0139] Experimental Example 2 - Evaluation of high-temperature storage characteristics The secondary batteries produced in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated for high-temperature storage characteristics.

[0140] Specifically, each of the secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 3 was fully charged to 4.2 V and then stored at 60° C. for 4 weeks.

[0141] Before storage, the volume of the fully charged secondary battery was measured and set as the initial thickness of the secondary battery.

[0142] After 4 weeks, the volume of the stored secondary battery was measured again, and the thickness increase during the 4-week storage period was calculated. The percentage of the increased volume relative to the initial volume of the secondary battery was calculated to derive the thickness increase rate after 4 weeks. The results are shown in Table 2 below.

[0143] [Table 2]

[0144] As shown in Table 2, the secondary batteries of Examples 1 to 6 showed a smaller thickness increase rate after 4 weeks and less gas generation at high temperatures than the secondary battery of Comparative Example 1. Furthermore, Examples 1 to 6, which used the nonaqueous electrolyte additive of the present invention in which electron-withdrawing groups are substituted at the 2- and 3-positions of the chromone, showed a smaller volume increase rate after 4 weeks and less gas generation at high temperatures than Comparative Example 2, which used an additive of Formula A with no substituents at the 2- and 3-positions of the chromone, and Comparative Example 3, which used an additive of Formula B in which electron-donating groups are substituted at the 2- and 3-positions of the chromone.

Claims

1. A non-aqueous electrolyte comprising an additive for a non-aqueous electrolyte represented by the following chemical formula 1: [Chemical formula 1] 【Chemical 1】 (In the above chemical formula 1, R １ and R ２ are each independently H; F; a nitrile group; a thiocyanate group; an isothiocyanate group; an isocyanate group; an alkoxycarbonyl group having 1 to 10 carbon atoms; an alkylcarbonyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms or a sulfonyl group substituted with an alkynyl group having 2 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms or an oxysulfonyl group substituted with an alkynyl group having 2 to 10 carbon atoms; CF ３ ;OCF ３ ;COOCF ３ and SO ２ CF ３ is any one selected from the group consisting of (provided that R １ and R ２ is also H), R ３ ~R ６ are each independently any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, and an aryl group having 6 to 20 carbon atoms.

2. The non-aqueous electrolyte according to claim 1, wherein the compound of Chemical Formula 1 is an additive for a non-aqueous electrolyte represented by the following Chemical Formula 1-1: [Chemical formula 1-1] 【Chemistry 2】 (In the above chemical formula 1-1, R １ and R ２ are each independently any one selected from the group consisting of H, F, an alkoxycarbonyl group having 1 to 10 carbon atoms, and a nitrile group (provided that R １ and R ２ (Except when both are H at the same time.)

3. 2. The non-aqueous electrolyte according to claim 1, wherein the compound of Chemical Formula 1 is any one selected from the group consisting of additives for non-aqueous electrolytes represented by the following Chemical Formulas 1-2a to 1-2h: [Chemical formula 1-2a] 【Chemistry 3】 [Chemical formula 1-2b] 【Chemistry 4】 [Chemical formula 1-2c] 【Chemistry 5】 [Chemical formula 1-2d] 【Chemistry 6】 [Chemical formula 1-2e] 【Chemistry 7】 [Chemical formula 1-2f] 【Chemistry 8】 [Chemical formula 1-2g] 【Chemistry 9】 [Chemical formula 1-2h] 【Chemistry 10】

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

5. The non-aqueous electrolyte according to claim 1 , further comprising a lithium salt.

6. The non-aqueous electrolyte according to claim 5 , wherein the lithium salt is contained at a concentration of 0.5 M to 2.0 M.

7. The lithium salts include LiCl, LiBr, LiI, and LiBF. ４ , LiClO ４ , LiB １０ Cl １０ , LiAlCl ４ , LiAlO ２ , LiPF ６ , LiCF ３ SO ３ , LiCH ３ CO ２ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiCH ３ SO ３ , LiN(SO ２ F) ２ , LiN(SO ２ CF ２ CF ３ ) ２ , and LiN(SO ２ CF ３ ) ２ The non-aqueous electrolyte according to claim 5 , wherein the non-aqueous electrolyte is one or more selected from the group consisting of:

8. The non-aqueous electrolyte according to claim 1 , further comprising an organic solvent.

9. 9. The nonaqueous electrolyte according to claim 8, wherein the organic solvent comprises at least one organic solvent 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.

10. 2. The nonaqueous electrolyte according to claim 1, further comprising, as other additives, one or more compounds 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.

11. A lithium secondary battery comprising the nonaqueous electrolyte according to claim 1 .

Images