Nonaqueous electrolyte and lithium secondary battery containing 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: JPEG2025507746000017.jpg83170 (In the above Chemical Formula 1, R1 may be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 8 carbon atoms, and R2 may be any one selected from the group consisting of an alkylene group having 1 to 10 carbon atoms and -OR3- (R3 is an alkylene group having 1 to 10 carbon atoms).)

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0129125, filed on October 7, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated as part of this specification.

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

[0003] In recent years, the application fields of lithium secondary batteries have expanded to various technical fields, and accordingly, there is an increasing demand for secondary batteries with high capacity, high output, and high stability.

[0004] In particular, when a secondary battery is operated at a high voltage to increase its capacity, as charging and discharging proceeds, the coating formed on the surface of the positive electrode / negative electrode or the structure of the electrode surface may deteriorate due to side reactions caused by the deterioration of the electrolyte, and transition metal ions may be eluted from the surface of the positive electrode. In this way, the eluted transition metal ions are electro-deposited on the negative electrode, which reduces the passivation ability of the SEI, causing the problem of the deterioration of the negative electrode.

[0005] Such deterioration of the secondary battery tends to be accelerated when the potential of the positive electrode is increased or when the battery is exposed to high temperatures.

[0006] In addition, when a lithium secondary battery is used continuously for a long period of time or left at high temperatures, gas is generated and the thickness of the battery increases, a phenomenon known as swelling. It is known that the amount of gas generated at this time depends on the state of the SEI.

[0007] Therefore, in order to solve these problems, research and development efforts are being conducted on methods that can reduce the swelling phenomenon of secondary batteries and improve their stability at high temperatures by suppressing the elution of metal ions in the positive electrode and forming a stable SEI film on the negative electrode. Summary of the Invention [Problem to be solved by the invention]

[0008] 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 uniform and dense SEI film on a negative electrode.

[0009] 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 durability at high temperatures.

[0010] 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 has improved performance. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a non-aqueous electrolyte comprising an additive for a non-aqueous electrolyte represented by the following chemical formula 1:

[0012] [ka]

[0013] In the above Chemical Formula 1, R1 may be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 8 carbon atoms, and R2 may be any one selected from the group consisting of an alkylene group having 1 to 10 carbon atoms and -OR3- (R3 is an alkylene group having 1 to 10 carbon atoms).

[0014] The present invention also provides a lithium secondary battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte. Effect of the Invention

[0015] The compound represented by Chemical Formula 1, which is provided as an additive for a non-aqueous electrolyte of the present invention, can form a polymeric, uniform and dense SEI (Solid Electrolyte Interphase) coating on the negative electrode. In particular, a propargyl group is substituted on the glycolide matrix, and the ring-opening reaction of glycolide and the reductive decomposition of the propargyl group occur simultaneously, so that a stronger polymeric coating can be formed. In addition, the additive represented by Chemical Formula 1 of the present invention can be decomposed at the positive electrode when the positive electrode reaches a high potential, thereby forming a positive electrode coating.

[0016] In other words, when a non-aqueous electrolyte containing the compound represented by Formula 1, which is provided as an additive for a non-aqueous electrolyte of the present invention, is contained in a lithium secondary battery, the decrease in passivation ability of SEI at high temperatures can be suppressed, and deterioration of the negative electrode can be prevented, thereby improving the life characteristics of the battery.

[0017] In addition, the compound represented by Formula 1, which is provided as an additive for a non-aqueous electrolyte of the present invention, can form a coating on the positive electrode when exposed to a high potential, thereby preventing the deterioration of the positive electrode.

[0018] Therefore, when the nonaqueous electrolyte of the present invention containing the compound of Chemical Formula 1 is used, an electrode-electrolyte interface that is stable even at high temperatures can be formed, thereby improving high-temperature cycle characteristics and high-temperature storage characteristics, and realizing a lithium secondary battery with improved performance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The terms and words used in this specification and the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a manner 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 describe their invention.

[0020] As used herein, terms such as "comprise," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but should not be understood as precluding the presence or additional possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0021] In the present specification, in the description of "number of carbon atoms a to b", "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 having 1 to 5 carbon atoms, i.e., -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2(CH3)CH-, -CH(CH3)CH2-, and -CH(CH3)CH2CH2-.

[0022] In addition, in this specification, the alkyl group may be either substituted or unsubstituted. The term "substituted" means that at least one hydrogen bonded to a carbon atom is substituted with an element other than hydrogen, and means that the alkyl group has 1 to 20 carbon atoms, the alkenyl group has 2 to 20 carbon atoms, the alkynyl group has 2 to 20 carbon atoms, the alkoxy group has 1 to 20 carbon atoms, the cycloalkyl group has 3 to 12 carbon atoms, the cycloalkenyl group has 3 to 12 carbon atoms, the heterocycloalkyl group has 3 to 12 carbon atoms, the heterocycloalkenyl group has 3 to 12 carbon atoms, the aryloxy group has 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group has 1 to 20 carbon atoms, a nitro group, an aryl group has 6 to 20 carbon atoms, a heteroaryl group has 2 to 20 carbon atoms, a haloaryl group has 6 to 20 carbon atoms, or the like.

[0023] The present invention will now be described in more detail.

[0024] Nonaqueous electrolyte The non-aqueous electrolyte according to the present invention contains, as an additive, a compound represented by the following chemical formula 1. A lithium secondary battery using a non-aqueous electrolyte containing the additive of the present invention is suppressed from deteriorating due to an interfacial reaction at high temperatures, and can have excellent high-temperature cycle characteristics and high-temperature storage characteristics.

[0025] [ka]

[0026] The compound of Formula 1 is decomposed and polymerized to form a uniform and dense polymeric coating on the surface of the negative electrode, and the coating formed in this manner can prevent deposition and electrodeposition due to dissolution of transition metals in the positive electrode, and can improve high-temperature durability and life characteristics. In addition, when a lithium secondary battery is exposed to a high potential, the compound of Formula 1 remaining after the formation of the negative electrode coating can form a coating on the positive electrode as well, thereby preventing deterioration due to oxidative decomposition of the electrolyte on the surface of the positive electrode.

[0027] In the above Chemical Formula 1, R1 may be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 8 carbon atoms. Preferably, in the above Chemical Formula 1, R1 may be H or an alkyl group having 1 to 10 carbon atoms, in which case, since the volume of the substituent is small, a denser coating can be formed.

[0028] In the above Chemical Formula 1, R2 may be any one selected from the group consisting of an alkylene group having 1 to 10 carbon atoms and -OR3- (R3 is an alkylene group having 1 to 10 carbon atoms), and preferably R2 may be any one selected from the group consisting of an alkylene group having 1 to 5 carbon atoms and -OR3- (R3 is an alkylene group having 1 to 5 carbon atoms).

[0029] Specifically, the compound of the present invention represented by Chemical Formula 1 may be any one selected from the group consisting of the following Chemical Formulas 1a to 1d.

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] The additive for non-aqueous electrolyte according to the present invention may be included in an amount of 0.01 to 5.0 parts by weight, preferably 0.1 to 3.0 parts by weight, and more preferably 0.5 to 1.0 parts by weight, relative to 100 parts by weight of the non-aqueous electrolyte. When the amount is within the above range, a sufficient amount of SEI can be formed, the viscosity of the electrolyte can be maintained at an appropriate level, and excellent rate characteristics and capacity characteristics can be obtained during high-temperature storage.

[0035] The lithium salt contained in the non-aqueous electrolyte of the present invention is used as an electrolyte salt in a lithium secondary battery and is used as a medium for transmitting ions. + and as an anion, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B10 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:

[0036] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10, 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, lithium salts commonly used in electrolytes for lithium secondary batteries can be used without any restrictions.

[0037] The lithium salt may be appropriately changed within a range that is normally usable, but in order to obtain an optimal effect of forming a corrosion prevention coating on the electrode surface, it may be contained in the electrolyte at a concentration of 0.5 M to 3 M, preferably a concentration of 0.5 M to 2.5 M, and more preferably a concentration of 0.8 M to 2 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate, so that the electrolyte impregnation can be improved.

[0038] The organic solvent contained in the nonaqueous electrolyte of the present invention 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.

[0039] Specifically, the organic solvent may include a cyclic carbonate organic solvent, a linear carbonate organic solvent, or a mixture thereof.

[0040] The cyclic carbonate organic solvent is a high-viscosity 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.

[0041] The linear carbonate organic solvent is an organic solvent having low viscosity and low dielectric constant, and a representative example thereof may be 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 may include ethyl methyl carbonate (EMC).

[0042] In addition, in order to produce an electrolyte having high ionic conductivity, the organic solvent may further contain at least one or more ester-based organic solvents selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents in addition to the at least one or more carbonate-based organic solvents selected from the group consisting of cyclic carbonate-based organic solvents and linear carbonate-based organic solvents.

[0043] 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.

[0044] 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.

[0045] Meanwhile, the organic solvent may be, if necessary, an organic solvent that is generally used in non-aqueous electrolytes without limitation, and may further include at least one of an ether-based organic solvent, a glyme-based solvent, and a nitrile-based organic solvent.

[0046] 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.

[0047] 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.

[0048] The nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0049] The nonaqueous electrolyte of the present invention may further contain a known electrolyte additive, as necessary, in order to prevent the nonaqueous electrolyte from being decomposed in a high-output environment, which would cause 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.

[0050] 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, 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.

[0051] The cyclic carbonate compounds include vinylene carbonate (VC), vinylethylene carbonate, and fluoroethylene carbonate.

[0052] 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.

[0053] The sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0054] The phosphate-based compound may be one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(2,2,2-trifluoroethyl)phosphite.

[0055] Examples of the borate-based compounds include tetraphenylborate, lithium oxalyl difluoroborate (LiODFB), and lithium bis(oxalate)borate (LiB(C2O4)2, LiBOB).

[0056] The nitrile compound may be 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.

[0057] The benzene-based compound may be fluorobenzene, the amine-based compound may be triethanolamine or ethylenediamine, and the silane-based compound may be tetravinylsilane.

[0058] The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples of the lithium salt-based compound include lithium difluorophosphate (LiDFP), LiPO2F2, and LiBF4.

[0059] Among these other electrolyte additives, when a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), and ethylene sulfate (Esa) is further included, a stronger SEI film can be formed on the surface of the negative electrode during the initial activation process of the secondary battery, and the generation of gas that may be generated by decomposition of the electrolyte at high temperatures can be suppressed, thereby improving the high temperature stability of the secondary battery.

[0060] On the other hand, the other electrolyte additives may be used in combination of two or more kinds, and may be included in an amount of 0.1 to 10 wt%, specifically 0.2 to 8 wt%, and preferably 0.5 to 8 wt%, based on the total weight of the non-aqueous electrolyte. When the content of the other electrolyte additives satisfies the above range, better ion conductivity and cycle characteristic improvement effects can be obtained.

[0061] Lithium secondary battery The present invention also provides a lithium secondary battery containing the non-aqueous electrolyte.

[0062] 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.

[0063] In this regard, the lithium secondary battery of the present invention may 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, and then inserting the electrode assembly into a battery case and injecting the non-aqueous electrolyte according to the present invention into the battery case.

[0064] The lithium secondary battery of the present invention has a driving voltage of 4.47 V or more and can be driven at a high voltage.

[0065] (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.

[0066] The positive 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 those obtained by surface treatment of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used.

[0067] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium metal oxide is a lithium-manganese-based oxide (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 p2Co q2 Mn r2 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 the respective independent elements, 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.

[0068] Among them, from the viewpoint of being able to improve 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.), lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), or lithium nickel manganese cobalt aluminum oxide (for example, Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2), etc. may be used, and any one or two or more of these mixtures may be used.

[0069] Among them, from the viewpoint of being able to maximize the capacity characteristics of the battery, a positive electrode active material having a nickel content of 80 atm% or more may be used. For example, the lithium transition metal oxide may include those represented by the following Chemical Formula 2.

[0070] [Chemical formula 2] Li x Ni a Co b M 1 c M 2 d O2

[0071] In the above Chemical Formula 2, M 1 is one or more selected from Mn and Al, and may be preferably Mn or a combination of Mn and Al from the viewpoint of durability.

[0072] 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.

[0073] 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.

[0074] The a represents the atomic fraction of nickel among the metal elements other than 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.

[0075] The b represents the atomic fraction of cobalt among the metal elements other than 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であってよい。

[0076] 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であってよい。

[0077] The d is the number of metal elements other than lithium in the lithium transition metal oxide, M 2 and may be 0≦d≦0.1, or 0≦d≦0.05.

[0078] 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 solid matter excluding the solvent in the positive electrode mixture slurry.

[0079] The binder is a component that assists in binding the active material and conductive material and the like to the current collector.

[0080] 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.

[0081] 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.

[0082] 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% by weight 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 a chemical change in the battery and has conductivity, and may be, for example, carbon powder such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; carbon fluoride powder; conductive powder such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives.

[0083] 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 excluding the solvent in the positive electrode mixture slurry.

[0084] 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 the positive electrode active material, and optionally a binder and a conductive material, etc. are contained. For example, the solvent may be contained so that the concentration of the solid content including the positive electrode active material, and optionally a binder and a conductive material, is 50 to 95% by weight, preferably 70 to 95% by weight, and more preferably 70 to 90% by weight.

[0085] (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.

[0086] For example, when the negative electrode is manufactured by coating the negative electrode mixture slurry on the negative electrode current collector, the negative electrode current collector generally has a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity, and for example, copper, stainless steel, aluminum, nickel, titanium, baked carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, as with the positive electrode current collector, the binding force of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and it can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric body, etc.

[0087] In addition, the negative electrode active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0088] The carbonaceous material capable of reversibly intercalating / deintercalating lithium ions may be any carbonaceous negative electrode active material commonly used in lithium ion secondary batteries, and representative examples thereof include crystalline carbon, amorphous carbon, or both. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0089] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn, or an alloy of these metals and lithium can be used.

[0090] 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) selected from the group can be used.

[0091] Examples of the substance capable of doping and undoping lithium include Si, SiO x (0 < x ≦ 2), Si-Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and a combination thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and a combination thereof, and is not Sn), etc. Also, at least one of these and SiO2 may be mixed and used. The element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and a combination thereof.

[0092] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

[0093] Among them, the negative electrode active material is SiO x (0 < x ≤ 2), or may be a mixture of graphite and SiO x (0 < x ≤ 2). From the viewpoint of increasing the capacity of the lithium secondary battery, the graphite and SiO x (0 < x ≤ 2) may be contained in a weight ratio of 100:0 to 70:30.

[0094] The negative electrode active material may be contained in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, more preferably 80 to 98% by weight, based on the total weight of the solid content in the negative electrode binder slurry.

[0095] The binder is a component that assists in binding 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, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers thereof, and the like.

[0096] Generally, the binder may be contained in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight, based on the total weight of the solid matter excluding the solvent in the negative electrode binder slurry.

[0097] 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% by weight 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 a chemical change in the battery and has conductivity, and may be, for example, carbon powder such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; 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; conductive materials such as polyphenylene derivatives, etc.

[0098] 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 excluding the solvent in the negative electrode mixture slurry.

[0099] 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 the negative electrode active material, and optionally a binder and a conductive material, etc. are included. For example, the solvent may be included so that the concentration of the solid content 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.

[0100] When a metal is used as the negative electrode, the negative electrode can be manufactured by physically bonding, rolling, or depositing a metal on a metal thin film or the negative electrode current collector. The deposition method can be an electrical deposition or chemical vapor deposition method.

[0101] For example, the metal thin film itself or the metal bonded / rolled / deposited onto 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).

[0102] (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 homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, which is used alone or in a laminated state, or a conventional porous nonwoven fabric, such as a nonwoven fabric made of a high melting point glass fiber, a polyethylene terephthalate fiber, etc., may be used, but is not limited thereto. In addition, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric substance may be used, and may be selectively used as a single layer or a multilayer structure.

[0103] 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.

[0104] 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 is obvious to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description, and it goes without saying that such changes and modifications belong to the scope of the attached claims.

[0105] Working Example Example 1 (Production of non-aqueous electrolyte) LiPF6 was dissolved in an organic solvent (ethylene carbonate (EC): dimethyl carbonate (DMC) = 20: 80 volume ratio) to a concentration of 1M to prepare a non-aqueous solvent, and 1 g of a compound represented by the following formula 1a was added to 99 g of the non-aqueous solvent to prepare a non-aqueous electrolyte.

[0106] [ka]

[0107] (manufacturing lithium secondary batteries) Cathode active material (LiNi 0.90 Co 0.03 Mn 0.06 Al 0.01 A cathode slurry (solid content 74 wt%) was prepared by adding the cathode material (O2), conductive material (carbon black), and binder (polyvinylidene fluoride) in a weight ratio of 97.5:1.3:1.2 to the solvent N-methyl-2-pyrrolidone (NMP). The cathode slurry was applied to one side of a cathode current collector (aluminum thin film) with a thickness of 130 μm, and dried and roll pressed to prepare a cathode.

[0108] Anode active material (graphite:SiO = 97:3 weight ratio), conductive material (carbon black), and binder (polyvinylidene fluoride) were added to a solvent, N-methyl-2-pyrrolidone (NMP), in a weight ratio of 96.8:0.2:3.0 to prepare anode slurry (solid content 60 wt%). The anode slurry was applied to one side of anode current collector (Cu thin film) with a thickness of 128 μm, and dried and roll pressed to prepare anode.

[0109] In a dry room, a porous polymer separator made of a polyolefin polymer was interposed between the positive electrode and the negative electrode prepared above, and then the non-aqueous electrolyte prepared above was injected to prepare a secondary battery.

[0110] Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 1 g of a compound represented by the following formula 1d was added to 99 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0111] [ka]

[0112] Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of the compound of Formula 1a was added to 99.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0113] Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that 3 g of the compound of Formula 1a was added to 97.5 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0114] Example 5 A secondary battery was manufactured in the same manner as in Example 1, except that 5 g of the compound of Formula 1a was added to 95 g of the nonaqueous solvent prepared in Example 1 to prepare a nonaqueous electrolyte.

[0115] Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared using 100 g of the non-aqueous solvent prepared in Example 1.

[0116] Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of 3,6-dimethyl-1,4-dioxane-2,5-dione was added to 99.5 g of the nonaqueous solvent manufactured in Example 1 to manufacture a nonaqueous electrolyte.

[0117] Experimental Example 1: Evaluation of high temperature cycle characteristics The cycle characteristics of each of the secondary batteries produced in Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated.

[0118] Specifically, the batteries manufactured in Examples 1 to 5 and Comparative Examples 1 and 2 were charged to 4.2 V at 45° C. in CC / CV mode at 1.0 C-rate, and discharged to 2.5 V at 1.0 C-rate in CC mode, counting as one cycle. After 200 charge / discharge cycles, the capacity retention rate relative to the initial capacity after one cycle was measured. The results are shown in Table 1 below.

[0119] [Table 1]

[0120] As shown in Table 1, it was confirmed that Examples 1 to 5 using the additive for non-aqueous electrolyte of the present invention had higher capacity retention after 200 cycles and improved life characteristics compared to Comparative Example 1 not using the additive. In particular, it was confirmed that the lithium secondary batteries of Examples 1 to 5 using the additive of Chemical Formula 1 of the present invention had better life characteristics compared to Comparative Example 2 using 3,6-dimethyl-1,4-dioxane-2,5-dione as an additive, which is not substituted with a propargyl group, unlike the additive for non-aqueous electrolyte of the present invention.

[0121] Experimental Example 2: Evaluation of high temperature storage characteristics For each of the secondary batteries produced in Examples 1 to 5 and Comparative Examples 1 and 2, high-temperature storage characteristics were evaluated.

[0122] Specifically, each of the secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2 was fully charged to 4.35 V and then stored at 60° C. for 6 weeks.

[0123] Before storage, the capacity of the fully charged secondary battery was measured and set as the initial capacity of the secondary battery.

[0124] After 6 weeks, the capacity of the stored secondary battery was measured, and the capacity loss during the 6-week storage period was calculated. The percentage of the lost capacity relative to the initial capacity of the secondary battery was calculated to derive the capacity retention rate after 6 weeks. The results are shown in Table 2 below.

[0125] [Table 2]

[0126] As shown in Table 2, it was confirmed that the secondary batteries of Examples 1 to 5 had higher capacity retention after 6 weeks and stable performance at high temperatures compared to the secondary battery of Comparative Example 1. In particular, it was confirmed that the lithium secondary batteries of Examples 1 to 5 using the additive of Chemical Formula 1 of the present invention had better high-temperature storage characteristics than Comparative Example 2 using 3,6-dimethyl-1,4-dioxane-2,5-dione as an additive, which is not substituted with a propargyl group, unlike the additive for non-aqueous electrolyte of the present invention.

Claims

1. A lithium salt; An organic solvent; A non-aqueous electrolyte comprising a compound represented by the following chemical formula 1 as an additive: 【Chemistry 1】 (In the above Chemical Formula 1, R １ is any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryl group having 6 to 8 carbon atoms; R ２ represents an alkylene group having 1 to 10 carbon atoms and -OR ３ - (R ３ is any one selected from the group consisting of an alkylene group having 1 to 10 carbon atoms.

2. R of Formula 1 １ The nonaqueous electrolyte according to claim 1, wherein is H or an alkyl group having 1 to 10 carbon atoms.

3. R of Formula 1 ２ is an alkylene group having 1 to 5 carbon atoms and -OR ３ - (R ３ 2. The nonaqueous electrolyte according to claim 1, wherein R is an alkylene group having 1 to 5 carbon atoms.

4. The non-aqueous electrolyte according to claim 1, wherein the compound of the formula 1 is any one selected from the group consisting of the following formulas 1a to 1d: 【Chemistry 2】 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】

5. 2. The non-aqueous electrolyte of claim 1, wherein the compound of Formula 1 is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

6. The lithium salts are LiCl, LiBr, LiI, and LiBF. ４ , LiClO ４ , LiB １０ C 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 1 , wherein the non-aqueous electrolyte is one or more selected from the group consisting of:

7. The non-aqueous electrolyte according to claim 1 , wherein the lithium salt is contained at a concentration of 0.5M to 3M.

8. 2. The nonaqueous electrolyte according to claim 1, wherein the organic solvent includes 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.

9. A positive electrode and A negative electrode; A lithium secondary battery comprising the nonaqueous electrolyte according to claim 1 .

10. The lithium secondary battery according to claim 9 , wherein the positive electrode contains a lithium nickel cobalt manganese oxide as a positive electrode active material.

11. The negative electrode contains graphite and SiO as a negative electrode active material. ｘ The lithium secondary battery according to claim 9 , wherein x is an integer of 0≦x<2.

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