Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery containing the same

Abstract

The present invention relates to a non-aqueous electrolyte for a lithium secondary battery containing a compound represented by Chemical Formula 1, a lithium salt, and an organic solvent; and a lithium secondary battery including the same.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0085817 filed on July 12, 2022, and Korean Patent Application No. 10-2023-0087775 filed on July 6, 2023, and all of its contents are incorporated herein by reference.

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

Background Art

[0003] A lithium secondary battery is generally manufactured by forming an electrode assembly with a separator interposed between a positive electrode including a positive electrode active material made of a transition metal oxide containing lithium and a negative electrode including a negative electrode active material capable of storing lithium ions, inserting the electrode assembly into a battery case, injecting a non-aqueous electrolyte serving as a medium for transmitting lithium ions, and then sealing it.

[0004] Lithium secondary batteries are applicable to various fields such as mobile devices, electronic products, and electric vehicles because they can be miniaturized and have high energy density and operating voltage. As the application fields of lithium secondary batteries become diverse, the required physical property conditions are gradually increasing. Specifically, the development of lithium secondary batteries that can stably operate even under high voltage / high temperature conditions and have long-life characteristics is required.

[0005] On the other hand, when a lithium secondary battery is driven under high voltage / high temperature conditions, the reaction in which anions such as PF6 in the electrolyte are decomposed may be enhanced to generate Lewis acids such as PF5, which may react with moisture to generate HF. Such decomposition products such as PF5 and HF can not only destroy the film formed on the surface of the electrode, but may also cause a decomposition reaction of the organic solvent, react with the decomposition products of the positive electrode active material to elute transition metal ions, and the eluted transition metal ions may be electrodeposited on the negative electrode to destroy the film formed on the surface of the negative electrode. - ​

[0006] When the electrolyte decomposition reaction continues on the film thus damaged, the performance of the battery further deteriorates. Therefore, there is a demand for the development of a secondary battery that can maintain excellent performance even under high voltage / high temperature conditions.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present invention is for solving the above problems, and aims to provide a non-aqueous electrolyte that contributes to forming a strengthened film on an electrode and a lithium secondary battery containing the same.

MEANS FOR SOLVING THE PROBLEMS

[0008] According to one embodiment, the present invention provides a non-aqueous electrolyte for a lithium secondary battery containing a lithium salt; an organic solvent; and a compound represented by the following Chemical Formula 1.

[0009]

Chem.

[0010] According to another embodiment, the present invention provides a lithium secondary battery including a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; a separator interposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte for the lithium secondary battery.

Effects of the Invention

[0011] The non-aqueous electrolyte according to the present invention contains a benzodioxane-based compound containing a substituent having an unsaturated bond, and thus has an effect of forming an ether-based film through an oxidation reaction at the positive electrode / negative electrode of a lithium secondary battery.

[0012] Since the ether-based film is superior in flexibility to a carbonate-based film, it is effective in suppressing film breakdown in a battery containing a Si-based negative electrode active material with a large volume change, and can suppress continuous decomposition of the electrolyte. Further, since the benzodioxane-based compound contains a benzene ring, it reacts quickly with reactive oxygen generated by a structural change of the positive electrode active material under high voltage driving conditions to suppress the oxidation reaction of the electrolyte, and finally can provide a lithium secondary battery with improved electrochemical characteristics.

Modes for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described in more detail.

[0014] Generally, anions contained in lithium salts such as LiPF6 widely used in electrolytes for lithium secondary batteries form decomposition products such as hydrogen fluoride (HF) and PF5 due to thermal decomposition or moisture. Such decomposition products have acidic properties and deteriorate the surface of the film or the electrode in the battery.

[0015] Due to decomposition products of the electrolyte and structural changes in the positive electrode caused by repeated charge and discharge, transition metals in the positive electrode are easily eluted into the electrolyte, and the eluted transition metals are re-deposited on the positive electrode again, increasing the resistance of the positive electrode. Not only that, when the eluted transition metals move to the negative electrode through the electrolyte, they electrodeposit on the negative electrode, causing the destruction of the SEI (solid electrolyte interphase) film and further electrolyte decomposition reactions, resulting in problems such as lithium ion consumption and increased resistance.

[0016] Also, when protective films are formed on the positive and negative electrodes by electrolyte reactions during the initial activation of the battery, if the films become unstable for the above reasons, further decomposition of the electrolyte occurs during charge and discharge or high-temperature exposure, accelerating the deterioration of the battery and generating gas.

[0017] As the demand for high-performance lithium secondary batteries increases, in order to increase the energy density, it is necessary to introduce Si-based negative electrode active materials with a much higher theoretical capacity compared to graphite. However, since Si-based negative electrode active materials have a very high volume change rate compared to graphite, in order to compensate for this disadvantage, it is necessary to form a film on the negative electrode that has strong durability and at the same time has flexible characteristics.

[0018] The driving voltage required to improve the energy density is also increasing, but there is a problem that the decomposition reaction of the electrolyte described above and the resulting deterioration of the battery performance become more serious during driving under high voltage.

[0019] In order to solve such problems, the inventors have found that by including a compound represented by the following Chemical Formula 1 in a non-aqueous electrolyte, the decomposition reaction of the electrolyte can be reduced through this, and the elution of transition metals and gas generation can be suppressed.

[0020] Specifically, the benzodioxane-based compound represented by the following Chemical Formula 1 contains an organic structure having an unsaturated bond, so it has the effect of improving the durability of the film by causing a polymerization reaction through a reaction with radicals generated by direct electrolysis or electrolyte decomposition on the surface of the electrode, and a flexible polymer film containing an oxygen-containing ring structure, that is, an ether structure through the decomposition of dioxane can be formed. It was confirmed that a long life can be achieved even in a battery to which a Si-based negative electrode active material with a large volume change is applied.

[0021] On the other hand, when driving the battery under a high voltage to increase the energy density, there is a problem that the decomposition rate of the electrolyte increases while reactive oxygen is desorbed due to the collapse of the positive electrode structure.

[0022] However, when the inventors include the compound represented by the following Chemical Formula 1 in the non-aqueous electrolyte, the benzene-ring structure contained in the compound can react with reactive oxygen faster than the electrolyte, so the decomposition of the electrolyte is suppressed, and it was confirmed that a long life can be achieved even under a high driving voltage of 4.25 V or more, specifically, 4.3 V or more.

[0023] Hereinafter, each configuration of the present invention will be described in more detail.

[0024] Non-aqueous electrolyte The present invention provides a non-aqueous electrolyte for a lithium secondary battery containing a lithium salt; an organic solvent; and a compound represented by Chemical Formula 1.

[0025] Hereinafter, each component will be specifically described.

[0026] (1) Compound represented by Chemical Formula 1 The non-aqueous electrolyte of the present invention contains a compound represented by the following Chemical Formula 1.

[0027]

Chemical formula

[0028] The oxygen-containing ring structure in the benzodioxane of Chemical Formula 1 increases the flexibility of the polymer contained in the coating while being decomposed, minimizing the coating decomposition at high temperatures. The benzene ring structure has the effect of enhancing the physical strength of the coating and reacting with reactive oxygen to suppress electrolyte decomposition.

[0029] However, when the dioxane ring does not contain a substituent or is substituted with a halogen group or oxygen (=O), gas-phase products may be generated due to the decomposition of dioxane. When the compound of Chemical Formula 1 contains an R1 substituent, the durability of the coating can be enhanced through the formation of a crosslinked polymer while reducing the gas generation amount. Specifically, the multiple bond between carbon and carbon or the multiple bond between carbon and a heteroatom in R1 can contribute to increasing the density of the coating formed on the electrode through polymerization.

[0030] In addition, the benzene ring in the benzodioxane of Chemical Formula 1 plays a role in binding to and removing reactive oxygen compounds. Since the R1 substituent is substituted on the dioxane ring rather than the benzene ring, it is preferable in that the above effects can be realized without interfering with the role of removing such reactive oxygen.

[0031] In one embodiment of the present invention, R1 in Chemical Formula 1 may be -COR, -COOR', -NCO, or a nitrile group.

[0032] Also, each of R and R' may independently be an alkyl group having 1 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms, and preferably may be a methyl group or a propargyl group. Preferably, R1 in Chemical Formula 1 is -COR or -COOR', and R and R' may be an alkenyl group having 2 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms. When a group containing a multiple bond in -CO- or -COO- is substituted in this way, it is advantageous for the formation of a film containing oxygen, and since the hopping of lithium ions is improved by the lone pair of oxygen, there is an effect of improving ionic conductivity and reducing the resistance of the battery. Also, when a multiple bond between carbon and carbon is included, it is advantageous for the formation of a crosslinked polymer through decomposition as compared with a substituent containing a multiple bond between carbon and nitrogen such as -NCO or a nitrile group, so the rate of increase in the resistance of the battery can be reduced.

[0033] On the other hand, R1 in Chemical Formula 1 may be -COCH3, -COO(CH2)CCH, -NCO, or a nitrile group, and more preferably may be -COO(CH2)CCH.

[0034] In still another embodiment of the present invention, R1 in Chemical Formula 1 is a substituent containing a multiple bond between carbon and carbon, that is, -COR, -COOR', an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms, while each of R and R' may independently be an alkenyl group having 2 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms.

[0035] In one embodiment of the present invention, the compound represented by Chemical Formula 1 may be represented by the following Chemical Formula 1-1.

[0036]

Chemical Formula

[0037] In one embodiment of the present invention, R2 may be the same substituent as R1, fluorine, or an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, and k may be 0 or 1. When R2 is substituted on the benzene ring in this way, it is preferable in terms of the aspect that the durability of the film formed on the electrode can be enhanced as the density of the film increases.

[0038] In one embodiment of the present invention, the Chemical Formula 1 may be represented by any one of the following Chemical Formulas 1A to 1D, and preferably may be represented by Chemical Formula 1A. Since the structure of Chemical Formula 1A contains a multiple bond between carbon and carbon, it is preferable in terms of the aspect that the durability of the film on the electrode can be enhanced as described above.

[0039]

Chemical formula

[0040]

Chemical formula

[0041]

Chemical formula

[0042]

Chemical formula

[0043] In terms of the aspect that the above-described effects of the input are sufficiently exhibited, the content of the compound represented by the Chemical Formula 1 may be 0.1% by weight or more, preferably 0.15% by weight or more, and more preferably 0.2% by weight or more based on the total weight of the non-aqueous electrolyte.

[0044] However, in terms of preventing a rapid increase in resistance due to excessive film formation, the content of the compound represented by Chemical Formula 1 may be 5% by weight or less, preferably 3% by weight or less, more preferably 1% by weight or less, based on the total weight of the non-aqueous electrolyte.

[0045] Most preferably, the content of the compound represented by Chemical Formula 1 may be 0.2% by weight or more and 0.5% by weight or less.

[0046] (2) Additive The non-aqueous electrolyte of the present invention can selectively further contain the following additives as necessary to prevent the electrolyte from being decomposed in a high-voltage environment and inducing the collapse of the electrode, or to further improve effects such as low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and suppression of battery swelling at high temperatures.

[0047] The additive may be any one or more selected from the group consisting of cyclic carbonate compounds, sultone compounds, sulfate compounds, phosphorus compounds, nitrile compounds, amine compounds, silane compounds, benzene compounds, and lithium salt compounds.

[0048] The cyclic carbonate compound may be any one or more selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and fluoroethylene carbonate (FEC), and specifically, it may be vinylene carbonate.

[0049] The sultone compound is a substance capable of forming a stable SEI film by a reduction reaction on the surface of the negative electrode, and may be any one or more selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, prop-1-ene-1,3-sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, and specifically, it may be 1,3-propane sultone (PS) or prop-1-ene-1,3-sultone (PRS).

[0050] The sulfate-based compound is a substance that can be electrically decomposed on the surface of the negative electrode to form a stable SEI film without cracks even during high-temperature storage, and may be any one or more selected from the group consisting of ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate (MTMS).

[0051] The phosphorus-based compound may be a phosphate-based or phosphite-based compound, and specifically, may be any one or more selected from the group consisting of tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite.

[0052] The nitrile-based compound may be any one or more selected from the group consisting of succinonitrile (SN), adiponitrile (ADN), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, ethylene glycol bis(2-cyanoethyl) ether (ASA3), 1,3,6-hexanetricarbonitrile (HTCN), 1,4-dicyano-2-butene (DCB), and 1,2,3-tris(2-cyanoethyl) propane (TCEP).

[0053] The amine-based compound may be any one or more selected from the group consisting of triethanolamine and ethylenediamine, and the silane-based compound may be tetravinylsilane.

[0054] The benzene-based compound may be any one or more selected from the group consisting of monofluorobenzene, difluorobenzene, trifluorobenzene, and tetrafluorobenzene.

[0055] The lithium salt-based compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and may be any one or more compounds selected from the group consisting of lithium difluorophosphate (LiDFP; LiPO2F2), lithium bis(oxalato)borate (LiBOB; LiB(C2O4)2), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate, lithium difluoro(oxalato)borate (LiDFOB), and lithium difluoro(bisoxalato)phosphate (LiDFOP).

[0056] Preferably, the non-aqueous electrolyte according to an embodiment of the present invention may further include any one or more additives selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), succinonitrile (SN), 1,3,6-hexanetricarbonitrile (HTCN), lithium difluoro(oxalato)borate (LiODFB), lithium tetrafluoroborate (LiBF4), 1,3-propane sultone (PS), prop-1-ene-1,3-sultone (PRS), ethylene sulfate (ESa), and lithium difluorophosphate (LiDFP). More preferably, it may include fluoroethylene carbonate. In this case, since the additive can form a film together with the compound represented by Chemical Formula 1 on the positive electrode and the negative electrode to enhance the durability of the film and at the same time reduce the resistance, the performance of the battery can be improved.

[0057] On the other hand, the content of the additive may be from 0.1% by weight to 10% by weight based on the total weight of the non-aqueous electrolyte, and preferably may be from 0.2% by weight to 5% by weight. When the content of the additive is within the above range, there is an effect of suppressing side reactions through the formation of a film on the positive electrode and the negative electrode.

[0058] (3) Organic solvent The non-aqueous electrolyte of the present invention contains an organic solvent.

[0059] As the organic solvent, various organic solvents usually used for lithium electrolytes may be used without limitation. For example, the organic solvent may be a cyclic carbonate solvent, a linear carbonate solvent, a linear ester solvent, a cyclic ester solvent, a nitrile solvent, or a mixture thereof, preferably, it can contain a mixture of two or more selected from the group consisting of a cyclic carbonate solvent, a linear carbonate solvent, and a linear ester solvent, and more preferably, it can contain a mixture of a cyclic carbonate solvent and a linear carbonate solvent.

[0060] The cyclic carbonate solvent is an organic solvent having a high viscosity and a high dielectric constant, so that it can well dissociate the lithium salt in the electrolyte, and it may be any one or more 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 preferably, it can contain ethylene carbonate (EC) or propylene carbonate (PC).

[0061] In addition, the linear carbonate solvent is an organic solvent having a low viscosity and a low dielectric constant, and it may be any one or more 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 preferably, it can contain ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or diethyl carbonate (DEC).

[0062] For producing an electrolytic solution having a high ionic conductivity, it is preferable to use a mixture of a cyclic carbonate solvent and a linear carbonate solvent as the organic solvent.

[0063] The linear ester solvent may be any one or more selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, and preferably may be methyl propionate, ethyl propionate, or propyl propionate.

[0064] The cyclic ester solvent may be any one or more selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0065] The nitrile solvent may be any one or more selected from the group consisting of succinonitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, and preferably may be succinonitrile.

[0066] Unless otherwise specified, the remaining components excluding the organic solvent among the total weight of the non-aqueous electrolytic solution, for example, the compound represented by the chemical formula 1, the additive, and the lithium salt content, may all be the organic solvent.

[0067] (4) Lithium salt The non-aqueous electrolytic solution of the present invention contains a lithium salt.

[0068] The lithium salt may be used without limitation as those commonly used in electrolytes for lithium secondary batteries. Specifically, the lithium salt contains 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 - , BF2C2O4CHF - , PF4C2O4 - , PF2C4O8 - , PO2F2 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and may contain any one or more selected from the group consisting of SCN - .

[0069] Specifically, the lithium salt may be any one or more selected from the group consisting of LiPF6, LiClO4, LiBF4, lithium bis(fluorosulfonyl)imide (LiN(FSO2)2; LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate (LiSO3CF3), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), lithium difluoro(bisoxalato)phosphate (LiDFOP), lithium tetrafluoro(oxalato)phosphate (LiTFOP), and lithium fluoromalonate(difluoro)borate (LiFMDFB), and preferably, it may be LiPF6.

[0070] In one embodiment of the present invention, the concentration of the lithium salt in the non-aqueous organic solution containing the lithium salt and the organic solvent may be from 0.5 M to 4.0 M, specifically, from 0.5 M to 3.0 M, and more specifically, from 0.8 M to 2.0 M. When the concentration of the lithium salt is within the above range, the effects of improving low-temperature output and cycle characteristics can be sufficiently ensured, and at the same time, it is possible to prevent the viscosity and surface tension from becoming excessively high and obtain appropriate electrolyte impregnation properties.

[0071] Lithium secondary battery Next, the lithium secondary battery according to the present invention will be described.

[0072] The lithium secondary battery according to the present invention includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. At this time, the non-aqueous electrolyte is the non-aqueous electrolyte according to the present invention. Since the non-aqueous electrolyte has been described above, the description thereof will be omitted, and hereinafter, other components will be described.

[0073] (1) Positive electrode The positive electrode according to the present invention contains a positive electrode active material, and can be manufactured by coating a positive electrode slurry containing the positive electrode active material, a binder, a conductive material, a solvent, etc. on a positive electrode current collector, and then drying and rolling.

[0074] The positive electrode current collector is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, stainless steel; aluminum; nickel; titanium; fired carbon; or those obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used.

[0075] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and may be one or more selected from LCO (LiCoO2); LNO (LiNiO2); LMO (LiMnO2); LiMn2O4, LiCoPO4; LFP (LiFePO4); and lithium composite transition metal oxides containing nickel (Ni), cobalt (Co), and manganese (Mn).

[0076] On the other hand, the positive electrode active material may be one in which the molar ratio of nickel among the transition metals is 60 mol% or more, preferably 70 mol% or more, and more preferably 80 mol% or more.

[0077] In one embodiment of the present invention, the lithium composite transition metal oxide may be a compound represented by the following Chemical Formula 2. That is, the positive electrode active material according to one embodiment of the present invention may contain a lithium composite transition metal oxide represented by the following Chemical Formula 2.

[0078] [Chemical Formula 2] Li 1+x (Ni a Co b Mn c M d )O2 In the Chemical Formula 2, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, 1 + x, a, b, c, and d are atomic fractions of independent elements, -0.2 ≤ x ≤ 0.2, 0.6 ≤ a < 1, 0 < b ≤ 0.3, 0 < c ≤ 0.3, 0 ≤ d ≤ 0.1, and a + b + c + d = 1.

[0079] The 1 + x indicates the lithium molar ratio in the lithium composite transition metal oxide, and it may be -0.1 ≤ x ≤ 0.2 or 0 ≤ x ≤ 0.2. When the lithium molar ratio satisfies the above range, the crystal structure of the lithium composite transition metal oxide can be stably formed.

[0080] The a indicates the molar ratio of nickel among the total metals excluding lithium in the lithium composite transition metal oxide, and it may be 0.70 ≤ a < 1, 0.75 ≤ a < 1, or 0.80 ≤ a < 1. When the nickel molar ratio satisfies the above range, it exhibits a high energy density and enables the realization of a high capacity.

[0081] The b indicates the molar ratio of cobalt among the total metals excluding lithium in the lithium composite transition metal oxide, and it may be 0 < b ≤ 0.20, 0 < b ≤ 0.18, or 0 < b ≤ 0.15. When the cobalt molar ratio satisfies the above range, good resistance characteristics and output characteristics can be realized.

[0082] The c indicates the molar ratio of manganese among the total metals excluding lithium in the lithium composite transition metal oxide, and it may be 0 < c ≤ 0.20, 0 < c ≤ 0.18, or 0 < c ≤ 0.15. When the manganese molar ratio satisfies the above range, excellent structural stability of the positive electrode active material can be obtained.

[0083] In one embodiment of the present invention, the lithium composite transition metal oxide may contain one or more doping elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. In other words, the d representing the molar ratio of the doping element among all the metals excluding lithium in the lithium composite transition metal oxide may be 0 < d ≤ 0.10, 0 < d ≤ 0.08, or 0 < d ≤ 0.05.

[0084] Preferably, a, b, c, and d in Chemical Formula 2 may be 0.70 ≤ a < 1, 0 < b ≤ 0.2, 0 < c ≤ 0.2, and 0 ≤ d ≤ 0.1, respectively.

[0085] In still another embodiment of the present invention, the lithium composite transition metal oxide is Li p Mn 1-q M q A2, Li p Mn2O 4-r X r , Li p Mn 2-q M q M’ r A4, Li p Co 1-q M q A2, Li p Co 1-q M q O 2-r X r , Li p Ni 1-q M q O 2-r X r , Li p Ni 1-q Co q O 2-r X r , Li p Ni 1-q-r Co q M r A w , Li p Ni 1-q-r Co q M r O 2-w X w , Li pNi 1-q-r Mn q M r A w and Li p Ni 1-q-r Mn q M r O 2-w X w may be any one or more selected from the group consisting of, wherein p, q, r, and w are respectively 0.9 ≦ p ≦ 1.2, 0 ≦ q ≦ 1, 0 ≦ r ≦ 1, 0 ≦ w ≦ 2, M and M' are the same as or different from each other, and are one or more elements selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V, and rare earth elements, A is one or more elements selected from the group consisting of O, F, S, and P, and X is one or more elements selected from the group consisting of F, S, and P.

[0086] The positive electrode active material may be contained in an amount of 80% by weight to 99% by weight, specifically 90% by weight to 99% by weight, based on the total weight of the solid content in the positive electrode slurry. At this time, when the content of the positive electrode active material is 80% by weight or less, the energy density may be low and the capacity may decrease.

[0087] The binder is a component that assists in binding the active material, conductive material, etc. and binding to the current collector, and may usually be added in an amount of 1% by weight to 30% by weight based on the total weight of the solid content in the positive electrode slurry. Examples of such binders may include polyvinylidene fluoride, 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, or various copolymers thereof.

[0088] Further, the conductive material is a substance that imparts conductivity without inducing a chemical change in the battery, and may be added in an amount of 0.5% by weight to 20% by weight based on the total weight of the solid content in the positive electrode slurry.

[0089] The conductive material may be selected from, for example, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, carbon nanotubes, and graphite; 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; and conductive materials such as polyphenylene derivatives.

[0090] Further, the solvent of the positive electrode slurry may contain an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a preferable viscosity when containing the positive electrode active material, binder, conductive material, and the like. For example, the concentration of the solid content in the positive electrode slurry containing the positive electrode active material, binder, and conductive material may be included so as to be 40% by weight to 90% by weight, preferably 50% by weight to 80% by weight.

[0091] (2) Negative electrode The negative electrode according to the present invention contains a negative electrode active material, and can be manufactured by coating a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, a solvent, and the like, followed by drying and rolling.

[0092] 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 has high conductivity without inducing chemical changes in the battery. For example, copper; stainless steel; aluminum; nickel; titanium; fired carbon; a surface-treated product of copper or stainless steel with carbon, nickel, titanium, silver, etc.; or an aluminum-cadmium alloy may be used. Similarly to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the binding force of the negative electrode active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0093] In one embodiment of the present invention, the negative electrode active material may contain a silicon-based material, and preferably, it may be composed of silicon, that is, pure silicon (Pure Si).

[0094] The silicon-based material is one or more selected from Si, SiO x (0 < x < 2), Si-Y alloy (wherein Y is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), and preferably, it is Si. 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 (Dubnium), 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. In the case of Si, SiO x has the advantage of having a high theoretical capacity relative to it.

[0095] Since the silicon-based negative electrode active material has a capacity nearly about 10 times higher than that of graphite, the mass loading (mg·cm -2) can be lowered to improve the rapid charging performance of the battery. However, there is a problem that it may affect the lifespan because the lithium ion loss rate due to the irreversible reaction is high and the volume change is large. However, such a problem can be solved by applying the non-aqueous electrolyte described above. Specifically, in the case of a negative electrode containing a silicon-based negative electrode active material, compared with a negative electrode containing only a carbon-based negative electrode active material, due to the large volume change during the charge and discharge process, there is a problem that the reaction in which the SEI film is easily cracked and regenerated continuously occurs. However, when the non-aqueous electrolyte according to the present invention is applied, the SEI film can be strengthened as described above, so such a problem can be effectively eliminated.

[0096] In one embodiment of the present invention, the silicon-based material may be contained in an amount of 5% by weight to 100% by weight, preferably 50% by weight to 100% by weight, more preferably 100% by weight, based on the total weight of the negative electrode active material. When the silicon-based material is contained within the above range, there is an effect of increasing the negative electrode capacity.

[0097] Further, the negative electrode active material may include, in addition to the silicon-based material, a carbon-based 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 undoping lithium; lithium metal; and one or more selected from transition metal oxides.

[0098] As the carbon-based material, any carbon-based negative electrode active material generally used in a lithium ion secondary battery can be used without particular limitation. Typical examples thereof include crystalline carbon, amorphous carbon, or both of these can 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 calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0099] 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 may be used.

[0100] As the metal composite oxide, 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, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), one or more selected from the group may be used.

[0101] Examples of the substance capable of doping and undoping lithium include 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). 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 (Dubnium), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Si, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0102] The negative electrode active material may be contained at 80% to 99% by weight based on the total weight of the solid content in the negative electrode slurry.

[0103] The binder is a component that aids in the binding between the conductive material, the active material, and the current collector, and may usually be added in an amount of 1% to 30% by weight based on the total weight of the solid content in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride, 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, or various copolymers thereof, and the like.

[0104] 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 0.5% to 20% by weight based on the total weight of the solid content in the negative electrode slurry. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, carbon nanotubes, and graphite; 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; and conductive materials such as polyphenylene derivatives, and the like may be selected therefrom.

[0105] The solvent of the negative electrode slurry may include water; or organic solvents such as NMP and alcohol, and may be used in an amount that provides a preferable viscosity when containing the negative electrode active material, the binder, the conductive material, and the like. For example, the concentration of the solid content in the slurry containing the negative electrode active material, the binder, and the conductive material may be included so as to be 30% to 80% by weight, preferably 40% to 70% by weight.

[0106] (3) Separator The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode.

[0107] The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions. Generally, any separator that can be used in a lithium secondary battery can be used without particular limitation. In particular, a separator having low resistance to ion migration of the electrolyte solution, excellent moisture retention ability of the electrolyte solution, and excellent safety is preferable.

[0108] Specifically, as the separator, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as a polyethylene homopolymer, a polypropylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer; or a laminate structure of two or more layers thereof may be used. Further, a normal porous nonwoven fabric, for example, a nonwoven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. may be used. Further, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance may be used, and it may be used in a single-layer or multilayer structure.

[0109] The lithium secondary battery according to the present invention as described above may be usefully used in the fields of portable devices such as mobile phones, notebook personal computers, digital cameras; and electric vehicles such as hybrid electric vehicles (HEV).

[0110] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same are provided.

[0111] The battery module or battery pack may be used as a power source for one or more medium to large-sized devices among power tools; electric vehicles including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); and power storage systems.

[0112] There is no particular limitation on the outer shape of the lithium secondary battery of the present invention, and it can be a cylindrical shape using a can, a rectangular shape, a pouch type, a coin type, or the like.

[0113] The lithium secondary battery according to the present invention can be used not only for battery cells used as a power source for small devices, but also preferably as a unit battery for medium to large-sized battery modules including a large number of battery cells.

[0114] Hereinafter, the present invention will be specifically described through specific examples.

Example

[0115] <Example: Production of Non-aqueous Electrolyte> Example 1. Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 30:70, and then dissolved so that LiPF6 was 1.2 M to produce a non-aqueous organic solution. 0.2 wt% of the compound represented by Chemical Formula 1A, 2 wt% of vinylene carbonate (VC), 5 wt% of fluoroethylene carbonate (FEC), and the remaining non-aqueous organic solution were mixed to produce 100 wt% of a non-aqueous electrolyte.

[0116] Example 2. A lithium secondary battery was produced in the same manner as in Example 1 except that the content of the compound represented by Chemical Formula 1A was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0117] Example 3. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the content of the compound represented by Chemical Formula 1A was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0118] Example 4. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the compound represented by Chemical Formula 1B was used instead of the compound represented by Chemical Formula 1A during the production of the non-aqueous electrolyte.

[0119] Example 5. A lithium secondary battery was manufactured in the same manner as in Example 4, except that the content of the compound represented by Chemical Formula 1B was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0120] Example 6. A lithium secondary battery was manufactured in the same manner as in Example 4, except that the content of the compound represented by Chemical Formula 1B was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0121] Example 7. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the compound represented by Chemical Formula 1C was used instead of the compound represented by Chemical Formula 1A during the production of the non-aqueous electrolyte.

[0122] Example 8. A lithium secondary battery was manufactured in the same manner as in Example 7, except that the content of the compound represented by Chemical Formula 1C was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0123] Example 9. A lithium secondary battery was manufactured in the same manner as in Example 7, except that the content of the compound represented by Chemical Formula 1C was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0124] Example 10. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the compound represented by Chemical Formula 1D was used instead of the compound represented by Chemical Formula 1A during the production of the non-aqueous electrolyte.

[0125] Example 11. A lithium secondary battery was manufactured in the same manner as in Example 10, except that the content of the compound represented by Chemical Formula 1D was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0126] Example 12. A lithium secondary battery was manufactured in the same manner as in Example 10, except that the content of the compound represented by Chemical Formula 1D was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0127] Comparative Example 1. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the compound represented by Chemical Formula 1A was not added during the production of the non-aqueous electrolyte.

[0128] Comparative Example 2. A lithium secondary battery was manufactured in the same manner as in Example 1, except that the compound represented by the following Chemical Formula Z1 was used instead of the compound represented by Chemical Formula 1A during the production of the non-aqueous electrolyte.

[0129]

Chemical Formula

[0130] Comparative Example 3. A lithium secondary battery was manufactured in the same manner as in Comparative Example 2, except that the content of the compound represented by Chemical Formula Z1 was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0131] Comparative Example 4. A lithium secondary battery was manufactured in the same manner as in Comparative Example 2, except that the content of the compound represented by Chemical Formula Z1 was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0132] Comparative Example 5 A lithium secondary battery was produced in the same manner as in Example 1, except that the compound represented by the following Chemical Formula Z2 was used instead of the compound represented by Chemical Formula 1A during the production of the non-aqueous electrolyte.

[0133]

Chem.

[0134] Comparative Example 6 A lithium secondary battery was produced in the same manner as in Comparative Example 5, except that the content of the compound represented by Chemical Formula Z2 was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0135] Comparative Example 7 A lithium secondary battery was produced in the same manner as in Comparative Example 5, except that the content of the compound represented by Chemical Formula Z2 was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0136] Comparative Example 8 A lithium secondary battery was produced in the same manner as in Example 1, except that the compound represented by the following Chemical Formula Z3 was used instead of the compound represented by Chemical Formula 1A during the production of the non-aqueous electrolyte.

[0137]

Chem.

[0138] Comparative Example 9 A lithium secondary battery was produced in the same manner as in Comparative Example 8, except that the content of the compound represented by Chemical Formula Z3 was changed to 1.0 wt% during the production of the non-aqueous electrolyte.

[0139] Comparative Example 10 A lithium secondary battery was produced in the same manner as in Comparative Example 8, except that the content of the compound represented by Chemical Formula Z3 was changed to 5.0 wt% during the production of the non-aqueous electrolyte.

[0140] <Experimental Example 1: Performance Evaluation of a Battery Containing a 100% Si Anode Material> Experimental Example 1-0. Manufacture of a Lithium Secondary Battery Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, a conductive material (carbon black), and a binder (polyvinylidene fluoride) were added in a weight ratio of 97.5:1:1.5 to produce a positive electrode slurry (solid content: 60% by weight). The positive electrode slurry was applied to and dried on an aluminum (Al) thin film, which is a positive electrode current collector with a thickness of 15 μm, and then roll press was performed to manufacture a positive electrode.

[0141] 100% Si as the anode active material, SBR-CMC as the binder, and carbon black as the conductive material were added in a weight ratio of 95:3.5:1.5 to water, which is a solvent, to produce a negative electrode slurry (solid content: 60% by weight). The negative electrode slurry was applied to and dried on a copper (Cu) thin film, which is a negative electrode current collector with a thickness of 6 μm, and then roll press was performed to manufacture a negative electrode.

[0142] The positive electrode, a polyolefin-based porous separator coated with inorganic particles (Al2O3), and the negative electrode were sequentially laminated to manufacture an electrode assembly.

[0143] The assembled electrode assembly was housed in a pouch exterior material, and the non-aqueous electrolyte solution manufactured in Examples 1 to 12 and Comparative Examples 1 to 10 was injected to manufacture a lithium secondary battery.

[0144] Experimental Example 1-1. Measurement of Capacity and Resistance after High-Temperature Storage After performing an activation (formation) process on each of the lithium secondary batteries manufactured in Experimental Example 1-0, constant current / constant voltage (CC / CV) charging (0.025C cut off) was performed up to 4.3V at a 0.33C rate at 25°C, and after discharging at a constant current (CC) up to 2.50V at a 0.33C rate, the initial discharge capacity and initial resistance were measured.

[0145] After that, the battery was fully charged to SOC 100% under the same conditions and stored at a high temperature (60°C) for 12 weeks. Then, after transferring it to a charger at room temperature (25°C), the capacity and resistance were measured again, and the capacity retention rate and resistance increase rate were calculated through the following formulas 1 and 2, and the results are shown in Table 1 below. Formula 1: Capacity retention rate (%) = (Discharge capacity after high-temperature storage / Initial discharge capacity) × 100 Formula 2: Resistance increase rate (%) = {(Resistance after high-temperature storage - Initial resistance) / Initial resistance} × 100

[0146] Experimental Example 1-2. Measurement of gas generation amount after high-temperature storage After performing the activation process on each lithium secondary battery manufactured in Experimental Example 1-0, charging (0.025C cut off) was carried out at a constant current / constant voltage condition up to 4.3V at a rate of 0.33C at 25°C, and it was fully charged to SOC 100%. After storing the fully charged battery at 60°C for 12 weeks and then transferring it to a charger at room temperature (25°C), the gas collected in the pouch was analyzed using GC-TCD (gas chromatography-thermal conductivity detector). When the gas generation amount measured in the battery containing the non-aqueous electrolyte of Comparative Example 1 was taken as 100%, the relative gas generation amounts of each other battery were calculated and shown in Table 1 below.

[0147] Experimental Example 1-3. High-temperature life evaluation After performing the activation process on each lithium secondary battery manufactured in Experimental Example 1-0, constant current / constant voltage (CC / CV) charging (0.025C cut off) was carried out up to 4.3V at a rate of 0.33C at 45°C, and discharging was carried out at a constant current (CC) up to 2.5V at a rate of 0.33C.

[0148] Regarding each charge / discharge performed once as one cycle, after repeating the same charge / discharge 300 times, the resistance increase rate (DCIR increase) and capacity retention rate were measured through the following formula 3. The measurement results are shown in Table 1 below. Formula 3: Capacity retention rate (%) = (Discharge capacity after 300 cycles / Discharge capacity after 1 cycle) × 100 Formula 4: Resistance increase rate (%) = { (Resistance after 300 cycles - Resistance after 1 cycle) / Resistance after 1 cycle} × 100

[0149]

Table 1

[0150] Through the results in Table 1 above, it can be confirmed that the batteries using the electrolytes of Examples 1 to 12 containing the compound of Chemical Formula 1 showed excellent results in all evaluation items, such as the capacity and resistance characteristics after high-temperature storage, the gas generation amount, and the capacity and resistance characteristics after high-temperature cycling, compared to the batteries using the electrolytes of Comparative Examples 1 to 10 that do not contain the compound of Chemical Formula 1.

[0151] In particular, when a compound of Chemical Formula 1A containing a propargyl group at the position of R1 was introduced as in Examples 1 to 3, the most excellent results were shown.

[0152] That is, not only Comparative Example 1 in which the compound represented by Chemical Formula 1 was not added, but also Comparative Examples 2 to 4 using unsubstituted benzodioxane instead of the compound of Chemical Formula 1, Comparative Examples 5 to 7 using fluorine-substituted benzodioxane, and Comparative Examples 8 to 10 using benzodioxane in which the benzene ring portion was substituted with an acetyl group (COCH3) had less favorable evaluation results compared to the batteries of Examples 1 to 12. Through this, it can be confirmed that the generation of gas that can occur due to electrochemical decomposition and the resulting deterioration of battery performance can be suppressed through the introduction of substituents.

[0153] <Experimental Example 2: Performance Evaluation of a Battery Containing a Graphite + Si Anode Material> Experimental Example 2-0. Manufacture of a Lithium Secondary Battery An electrode assembly was manufactured in the same process as in Experimental Example 1-0, except that a negative electrode active material in which 97.5 wt% of natural graphite and 2.5 wt% of Si were mixed was used instead of the negative electrode active material with 100% Si during the manufacture of the negative electrode.

[0154] The assembled electrode assembly was housed in the pouch exterior material, and a non-aqueous electrolyte solution produced in Examples 1 to 4, 7, and 10 and Comparative Examples 1, 2, 5, and 8 was injected to manufacture a lithium secondary battery.

[0155] Experimental Example 2-1. Measurement of Capacity and Resistance after High-Temperature Storage For each of the lithium secondary batteries manufactured in Experimental Example 2-0, the same process as in Experimental Example 1-1 was carried out to obtain the capacity retention rate and the resistance increase rate, and the results are shown in Table 2 below.

[0156] Experimental Example 2-2. Measurement of Gas Generation Amount after High-Temperature Storage For each of the lithium secondary batteries manufactured in Experimental Example 2-0, the gas generation amount after high-temperature storage was obtained in the same process as in Experimental Example 1-2, and this is shown in Table 2 below.

[0157] Experimental Example 2-3. Evaluation of High-Temperature Life For each of the lithium secondary batteries manufactured in Experimental Example 2-0, the high-temperature life was measured in the same process as in Experimental Example 1-3, and the results are shown in Table 2 below.

[0158]

Table 2

[0159] Through the results in Table 2 above, it can be confirmed that for the batteries using the electrolytes of Examples 1 to 4, 7, and 10 containing the compound of Chemical Formula 1, even when the negative electrode material was changed, they showed excellent results in all evaluation items such as the capacity and resistance characteristics after high-temperature storage, the gas generation amount, and the capacity and resistance characteristics after high-temperature cycling, compared with the batteries using the electrolytes of Comparative Examples 1, 2, 5, and 8 that do not contain the compound of Chemical Formula 1.

[0160] <Experimental Example 3: Performance Evaluation of Batteries Containing the Cathode Material of NCM613> Experimental Example 3-0. Manufacture of Lithium Secondary Batteries During the manufacture of the cathode, the composition was Li(Ni0.8 Co 0.1 Mn 0.1 )O2 as the positive electrode active material was replaced with Li(Ni 0.6 Co 0.1 Mn 0.3 )O2 as the positive electrode active material, an electrode assembly was manufactured in the same process as in the above Experimental Example 1-0, except for this.

[0161] The assembled electrode assembly was housed in a pouch exterior material, and a non-aqueous electrolyte solution manufactured in the above Examples 1 to 4, 7, and 10 and Comparative Examples 1, 2, 5, and 8 was injected to manufacture a lithium secondary battery.

[0162] Experimental Example 3-1. Measurement of Capacity and Resistance after High-Temperature Storage For each of the lithium secondary batteries manufactured in the above Experimental Example 3-0, except that the upper limit voltage was changed from 4.3 V to 4.4 V, the same process as in the above Experimental Example 1-1 was performed to obtain the capacity retention rate and the resistance increase rate, and the results are shown in Table 3 below.

[0163] Experimental Example 3-2. Measurement of Gas Generation Amount after High-Temperature Storage For each of the lithium secondary batteries manufactured in the above Experimental Example 3-0, except that the upper limit voltage was changed from 4.3 V to 4.4 V, the gas generation amount after high-temperature storage was obtained in the same process as in the above Experimental Example 1-2, and this is shown in Table 3 below.

[0164] Experimental Example 3-3. Evaluation of High-Temperature Life For each of the lithium secondary batteries manufactured in the above Experimental Example 3-0, except that the upper limit voltage was changed from 4.3 V to 4.4 V, the high-temperature life was measured in the same process as in the above Experimental Example 1-3, and the results are shown in Table 3 below.

[0165]

Table 3

[0166] Through the results in Table 3, it can be confirmed that the batteries using the electrolytes of Examples 1 to 4, 7, and 10 containing the compound of Chemical Formula 1 showed excellent results in all evaluation items, such as the capacity and resistance characteristics after high-temperature storage, the gas generation amount, and the capacity and resistance characteristics after high-temperature cycling, compared with the batteries using the electrolytes of Comparative Examples 1, 2, 5, and 8 that do not contain the compound of Chemical Formula 1, even when the cathode material was changed.

Claims

1. A non-aqueous electrolyte for a lithium secondary battery comprising a lithium salt, an organic solvent, and a compound represented by the following Chemical Formula 1: 【Chemical 1】 In Chemical Formula 1 above, R1 is -COR, -COOR', -NCO, a nitrile group, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms, R2 is a halogen group; -COR''; -COOR'''; -NCO; a nitrile group; an alkyl group having 1 to 10 carbon atoms substituted or unsubstituted with one or more halogen groups; an alkenyl group having 2 to 10 carbon atoms; or an alkynyl group having 2 to 10 carbon atoms, R, R', R'', and R''' are each independently hydrogen, 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, n is 1 or 2, and when n is 2, the two R1s are the same as or different from each other, m is any integer from 0 to 8 - n.

2. The non-aqueous electrolyte for a lithium secondary battery according to Claim 1, wherein R1 is -COR, -COOR', -NCO, or a nitrile group.

3. The non-aqueous electrolyte for a lithium secondary battery according to Claim 1, wherein R and R' are each independently an alkyl group having 1 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms.

4. The non-aqueous electrolyte for a lithium secondary battery according to Claim 1, wherein the compound represented by Chemical Formula 1 is represented by the following Chemical Formula 1-1: 【Chemical 2】 In Chemical Formula 1-1 above, R1 and R2 are as defined in Chemical Formula 1, k is an integer from 0 to 4.

5. The non-aqueous electrolyte for a lithium secondary battery according to Claim 1, wherein the content of the compound represented by Chemical Formula 1 is 0.1% by weight or more and 5% by weight or less based on the total weight of the non-aqueous electrolyte.

6. The non-aqueous electrolyte for a lithium secondary battery according to Claim 1, wherein the content of the compound represented by Chemical Formula 1 is 0.15% by weight or more and 3% by weight or less based on the total weight of the non-aqueous electrolyte.

7. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, further comprising any one or more additives selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinonitrile, 1,3,6-hexanetricarbonitrile, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, 1,3-propane sultone, prop-1-ene-1,3-sultone, ethylene sulfate, and lithium difluorophosphate.

8. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the organic solvent contains a mixture of two or more selected from the group consisting of cyclic carbonate solvents, linear carbonate solvents, and linear ester solvents.

9. A positive electrode containing a positive electrode active material; A negative electrode containing a negative electrode active material; A separator interposed between the positive electrode and the negative electrode; and A lithium secondary battery containing the non-aqueous electrolyte according to any one of claims 1 to 8.

10. The lithium secondary battery according to claim 9, wherein the positive electrode active material contains a lithium composite transition metal oxide represented by the following Chemical Formula 2: [Chemical Formula 2] Li １＋ｘ (Ni ａ Co ｂ Mn ｃ M ｄ )O ２ In the Chemical Formula 2, M is one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, 1 + x, a, b, c, and d are atomic fractions of independent elements, respectively, -0.2 ≦ x ≦ 0.2, 0.6 ≦ a < 1, 0 < b ≦ 0.3, 0 < c ≦ 0.3, 0 ≦ d ≦ 0.1, and a + b + c + d = 1.

11. The lithium secondary battery according to claim 10, wherein a, b, c, and d in the Chemical Formula 2 are 0.70 ≦ a < 1, 0 < b ≦ 0.2, 0 < c ≦ 0.2, and 0 ≦ d ≦ 0.1, respectively.

12. The lithium secondary battery according to claim 9, wherein the negative electrode active material contains a silicon-based material.

13. The lithium secondary battery according to claim 12, wherein the negative electrode active material consists of silicon.

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