Electrolyte additive, electrolyte for lithium secondary battery containing the same, and lithium secondary battery

Abstract

The present invention relates to a sultone compound; LiPO 2 F 2 and a compound represented by Chemical Formula 1; an electrolyte additive comprising the electrolyte additive; and a lithium secondary battery comprising the electrolyte.

Description

Technical Field

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0142005, filed with the Korean Intellectual Property Office on October 22, 2021, and all of its contents are incorporated herein by reference.

[0002] The present invention relates to an electrolyte additive, an electrolyte for a lithium secondary battery including the same, and a lithium secondary battery.

Background Art

[0003] In recent years, with the rapid spread of electronic devices using batteries such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries that are small and light but relatively high in capacity has been rapidly increasing. In particular, lithium secondary batteries are lightweight and have a high energy density, and have been in the spotlight as a driving power source for portable devices. Therefore, efforts have been actively made for research and development to improve the performance of lithium secondary batteries.

[0004] Generally, a lithium secondary battery is composed of a carbon material or a silicon-based negative electrode capable of intercalating and deintercalating lithium ions, a positive electrode composed of a lithium-containing transition metal oxide, and a non-aqueous electrolyte. During the first charge, lithium ions released from the positive electrode active material are inserted into the negative electrode active material, and during discharge, they are desorbed again, etc. By reciprocating between both electrodes to transfer energy, charging and discharging become possible.

[0005] However, as charging and discharging proceed, the positive electrode active material structurally collapses, resulting in a decrease in the performance of the positive electrode. In addition, metal ions eluted from the surface of the positive electrode during the collapse of the positive electrode structure are electrodeposited on the negative electrode, deteriorating the negative electrode. Such a battery performance degradation phenomenon tends to be further accelerated when the potential of the positive electrode increases or the battery is exposed to high temperatures.

[0006] In order to solve such problems, a method has been proposed in which a compound capable of forming a protective film that can suppress metal elution and dendrites on the surface of an electrode is added to a non-aqueous electrolyte. However, side effects may occur due to the compound added to the electrolyte, and various performances of the secondary battery may decrease.

[0007] In addition, the discrimination criterion for low voltage in the open circuit voltage (OCV) distribution after the completion of the battery activation process is within the range of normal voltage ±2 mV. When the distribution of the open circuit voltage shows a bimodal curve or a broad distribution, the battery is determined to be defective, causing a problem of very low yield.

[0008] Therefore, there is a continuing need for the development of an electrolyte containing an additive that can increase the battery yield without reducing the battery performance and stability while minimizing side effects.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention aims to provide an electrolyte additive, an electrolyte for a lithium secondary battery containing the same, and a lithium secondary battery.

Means for Solving the Problems

[0010] One embodiment of the present invention provides an electrolyte additive containing a sultone compound; LiPO2F2; and a compound represented by the following Chemical Formula 1. [Chemical Formula 1]

Chem.

[0011] One embodiment of the present invention provides an electrolyte for a lithium secondary battery, which includes a lithium salt, an organic solvent, and the electrolyte additive.

[0012] One embodiment of the present invention provides a lithium secondary battery including the electrolyte for a lithium secondary battery.

Advantages of the Invention

[0013] The electrolyte additive according to one embodiment of the present invention has the effect of improving the open circuit voltage (OCV) distribution after the completion of the activation process and increasing the battery yield without degrading the battery performance and stability.

Brief Description of the Drawings

[0014]

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Embodiments for Carrying Out the Invention

[0015] Hereinafter, this specification will be described in more detail.

[0016] In this specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components, but may further include other components.

[0017] In this specification, when a certain member is said to be "on" another member, this includes not only the case where a certain member is in contact with another member, but also the case where there are other members between the two members.

[0018] The terms and words used in this specification should not be construed as being limited to their ordinary or dictionary meanings. The inventors should interpret them in accordance with the principle that they can appropriately define the concepts of the terms in order to explain their invention in the best way, and should interpret them in meanings and concepts consistent with the technical idea of the present invention.

[0019] The singular expressions of the terms used in this specification include plural expressions unless the context clearly indicates otherwise.

[0020] In this specification, examples of substituents will be described below, but are not limited thereto.

[0021] The term "substitution" means that a hydrogen atom bonded to a carbon atom of a compound is replaced by another substituent, and the position to be substituted is not limited as long as it is the position where the hydrogen atom is substituted, i.e., the position where the substituent can be substituted. When two or more substitutions occur, the two or more substituents may be the same or different from each other.

[0022] As used herein, the term "substituted or unsubstituted" means being substituted with one or more substituents selected from the group consisting of deuterium; a halogen group; a nitrile group (-CN); a nitro group; a hydroxy group; an alkyl group; an aryl group; or a heterocyclic group, being substituted with a substituent in which two or more of the exemplified substituents are linked, or having no substituents. For example, the "substituent in which two or more substituents are linked" may be a biphenyl group. That is, the biphenyl group may be an aryl group and can be interpreted as a substituent in which two phenyl groups are linked.

[0023] As used herein, the alkyl group may be linear or branched, and its carbon number is not particularly limited, but is preferably 1 to 60. According to one embodiment, the carbon number of the alkyl group is 1 to 30. According to another embodiment, the carbon number of the alkyl group is 1 to 20. According to another embodiment, the carbon number of the alkyl group is 1 to 10. Specific examples of the alkyl group include, but are not limited to, methyl group, ethyl group, propyl group, n-propyl group, isopropyl group, butyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, n-pentyl group, hexyl group, n-hexyl group, heptyl group, n-heptyl group, octyl group, n-octyl group, etc.

[0024] In this specification, the alkenyl group may be linear or branched, and the number of carbon atoms is not particularly limited, but is preferably 2 to 40. According to one embodiment, the number of carbon atoms of the alkenyl group is 2 to 20. According to another embodiment, the number of carbon atoms of the alkenyl group is 2 to 10. According to another embodiment, the number of carbon atoms of the alkenyl group is 2 to 6. Specific examples include vinyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 3-methyl-1-butenyl, 1,3-butadienyl, allyl, 1-phenylvinyl-1-yl, 2-phenylvinyl-1-yl, 2,2-diphenylvinyl-1-yl, 2-phenyl-2-(naphthyl-1-yl)vinyl-1-yl, 2,2-bis(diphenyl-1-yl)vinyl-1-yl, styrenyl group, etc., but are not limited thereto.

[0025] In this specification, the alkynyl group is a substituent containing a triple bond between carbon atoms, and may be linear or branched, and the number of carbon atoms is not particularly limited, but is preferably 2 to 40. According to one embodiment, the number of carbon atoms of the alkynyl group is 2 to 20. According to another embodiment, the number of carbon atoms of the alkynyl group is 2 to 10.

[0026] In this specification, the aryl group is not particularly limited, but preferably has 6 to 60 carbon atoms, and may be a monocyclic aryl group or a polycyclic aryl group. According to one embodiment, the number of carbon atoms of the aryl group is 6 to 30. According to one embodiment, the number of carbon atoms of the aryl group is 6 to 20. The aryl group, as a monocyclic aryl group, includes, but is not limited to, phenyl group, biphenyl group, terphenyl group, quarterphenyl group, etc. The polycyclic aryl group includes, but is not limited to, naphthyl group, anthracenyl group, phenanthrenyl group, pyrenyl group, perylenyl group, triphenylenyl group, chrysenyl group, fluorenyl group, triphenylenyl group, etc.

[0027] In this specification, a heterocyclic group is a cyclic group containing one or more of N, O, P, S, Si, and Se as heteroatoms, and the number of carbon atoms is not particularly limited, but is preferably 2 to 60. According to one embodiment, the number of carbon atoms of the heterocyclic group is 2 to 30. According to one embodiment, the number of carbon atoms of the heterocyclic group is 2 to 20. Examples of the heterocyclic group include, but are not limited to, a pyridine group, a pyrrole group, a pyrimidine group, a quinoline group, a pyridazinyl group, a furan group, a thiophene group, an imidazole group, a pyrazole group, a dibenzofuran group, a dibenzothiophene group, a carbazole group, a benzocarbazole group, a naphthobenzofuran group, a benzonaphthothiophene group, an indenocarbazole group, a triazinyl group, and the like.

[0028] In this specification, an alkylene group may be subject to the description of the alkyl group, except that it is a divalent group.

[0029] In this specification, an alkenylene group may be subject to the description of the alkenyl group, except that it is a divalent group.

[0030] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the embodiments of the present invention may be modified into various forms, and the scope of the present invention is not limited to the embodiments described below.

[0031] One embodiment of the present invention provides an electrolyte additive containing a sultone-based compound; LiPO2F2; and a compound represented by the following Chemical Formula 1. [Chemical Formula 1]

Chemical Formula

[0032] Generally, in the open circuit voltage (OCV) distribution after the completion of the battery activation process, when the discrimination criterion for low voltage is within the range of normal voltage ±2 mV and the OCV distribution shows a bimodal curve or a wide distribution, the battery is determined to be defective, which causes a problem of extremely low yield.

[0033] The battery using the electrolyte additive according to an embodiment of the present invention shows a very sharp shape in the OCV distribution after the completion of the activation process, so it can contribute to the improvement of the yield.

[0034] Generally, if the film resistance of the negative electrode is excessively large, a deviation occurs in the charged state of the battery, and the OCV distribution after the first charge becomes wide, so the OCV distribution after the final activation process becomes wide. On the contrary, if the film resistance of the negative electrode is excessively small, a deviation in self-discharge occurs during high-temperature aging, and the OCV distribution after high-temperature aging becomes large, so the OCV distribution after the final activation process becomes wide.

[0035] Since the sultone-based compound increases the film resistance of the negative electrode, when only the sultone-based compound is applied to the electrolyte, there is a problem that the resistance of the battery becomes extremely large. On the contrary, since the compound of Chemical Formula 1 is reduced earlier than the sultone-based compound in the electrolyte, the influence of the resistance by the sultone-based compound can be suppressed. However, the film formed thereby has a problem that the ability to suppress reduction in the electrolyte is low and the self-discharge of the battery becomes large.

[0036] Therefore, when only the sultone-based compound and the compound of Chemical Formula 1 are used, there is a problem that the film resistance becomes excessively low, the OCV distribution after the battery activation process becomes large due to the deviation of self-discharge, and the yield decreases.

[0037] LiPO2F2 can form a film well, but its self-discharge suppression property is not sufficient, and it cannot suppress the influence of sultone compounds. Therefore, when only sultone compounds and LiPO2F2 are used, the film resistance becomes excessively large, and the OCV distribution during battery charging also increases. As a result, even after the activation process, there is a wide OCV distribution, and there is a problem of reduced yield.

[0038] In contrast, when using the electrolyte additive of the present invention that simultaneously contains a sultone compound, LiPO2F2, and the compound of Chemical Formula 1, an optimal film resistance can be obtained, and the OCV distribution after the activation process of the battery is improved sharply (Sharp). Therefore, there is an effect that the yield of the battery also increases.

[0039] In one embodiment of the present invention, the electrolyte additive contains a compound represented by the following Chemical Formula 1. [Chemical Formula 1]

Chemical Formula

[0040] In one embodiment of the present invention, the R1 is hydrogen; an alkyl group having 1 to 10 carbon atoms; or an aryl group having 6 to 30 carbon atoms.

[0041] In one embodiment of the present invention, the R1 is an alkyl group having 1 to 10 carbon atoms.

[0042] In one embodiment of the present invention, the R1 is an alkyl group having 1 to 5 carbon atoms.

[0043] In one embodiment of the present invention, the R1 is a methyl group; an ethyl group; a propyl group; a butyl group; or a pentyl group.

[0044] In one embodiment of the present invention, R1 is a methyl group.

[0045] In one embodiment of the present invention, L1 is an alkylene group having 1 to 10 carbon atoms.

[0046] In one embodiment of the present invention, L1 is an alkylene group having 1 to 5 carbon atoms.

[0047] In one embodiment of the present invention, L1 is a methylene group; an ethylene group; a propylene group; a butylene group; or a pentylene group.

[0048] In one embodiment of the present invention, L1 is a methylene group.

[0049] In one embodiment of the present invention, the compound represented by Chemical Formula 1 is methyl prop-2-yn-1-yl carbonate.

[0050] In one embodiment of the present invention, the compound represented by Chemical Formula 1 is represented by the following compound.

Chemical Formula

[0051] The electrolyte additive according to one embodiment of the present invention contains a sultone compound.

[0052] In one embodiment of the present invention, the sultone compound may include a structure including a cyclic sulfonic ester. Specifically, it may include a compound represented by the following Chemical Formula 2. [Chemical Formula 2]

Chemical Formula

[0053] In one embodiment of the present invention, L2 is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms substituted with an alkyl group having 1 to 10 carbon atoms; or a substituted or unsubstituted alkenylene group having 2 to 10 carbon atoms substituted with an alkyl group having 1 to 10 carbon atoms.

[0054] In one embodiment of the present invention, L2 is an ethylene group substituted or unsubstituted with a methyl group; a propylene group substituted or unsubstituted with a methyl group; a butylene group substituted or unsubstituted with a methyl group; a vinylene group substituted or unsubstituted with a methyl group; or a propenylene group substituted or unsubstituted with a methyl group.

[0055] In one embodiment of the present invention, L2 is a methylene group; a propylene group; a vinylene group; or a propenylene group.

[0056] In one embodiment of the present invention, n is from 1 to 3.

[0057] The sultone compound may be 1,3 - propane sultone, 1,4 - butane sultone, ethene sultone, 1 - propene 1,3 - sultone, preferably 1,3 - propane sultone, 1 - propene 1,3 - sultone, or a mixture of 1,3 - propane sultone and 1 - propene 1,3 - sultone.

[0058] In one embodiment of the present invention, the sultone compound may be one or more selected from the group consisting of 1,3 - propane sultone and 1 - propene 1,3 - sultone.

[0059] The above 1,3 - propane sultone is [Chemical formula] as follows.

[0060] The above 1 - propene 1,3 - sultone is [Chemical formula] as follows.

[0061] Specifically, when using the above compound, there is a tendency to increase the film resistance of the negative electrode.

[0062] The electrolyte additive according to an embodiment of the present invention contains LiPO2F2.

[0063] In one embodiment of the present invention, the sultone - based compound may be contained in an amount of 10 parts by weight to 50 parts by weight based on 100 parts by weight of the electrolyte additive. In another embodiment, it may be contained in an amount of 14 parts by weight to 46 parts by weight, or 25 parts by weight to 30 parts by weight. When the content of the sultone - based compound is less than the above range, a sufficient film - forming effect cannot be obtained, and there is a problem that side effects occur during high - temperature aging and the OCV distribution becomes large. On the contrary, when the content of the sultone - based compound exceeds the above range, the interfacial resistance becomes large, and there is a problem that a deviation in the charged state occurs during charging and the OCV distribution becomes large.

[0064] In one embodiment of the present invention, the LiPO2F2 may be contained in an amount of 30 to 80 parts by weight based on 100 parts by weight of the electrolyte additive. In another embodiment, it may be contained in an amount of 40 to 75 parts by weight, or may be contained in an amount of 55 to 65 parts by weight. When the content of LiPO2F2 is less than the above range, the interfacial resistance cannot be sufficiently reduced, and there is a problem that a deviation in the state of charge occurs during charging and the OCV distribution becomes large. On the other hand, when the content of LiPO2F2 exceeds the above range, the interfacial resistance becomes excessively small, and there is a problem that side effects occur during high-temperature aging and the OCV distribution becomes large.

[0065] In one embodiment of the present invention, the compound represented by Chemical Formula 1 may be contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of the electrolyte additive. In another embodiment, it may be contained in an amount of 3 to 27 parts by weight, or may be contained in an amount of 10 to 12 parts by weight. When the content of the compound represented by Chemical Formula 1 is less than the above range, the sultone compound preferentially forms a film over the compound represented by Chemical Formula 1, increasing the interfacial resistance, and there is a problem that a deviation in the state of charge occurs during charging and the OCV distribution becomes large. On the other hand, when the content of the compound represented by Chemical Formula 1 exceeds the above range, the film-forming reaction of the sultone compound is excessively suppressed, and a sufficient interfacial resistance cannot be obtained, and there is a problem that side effects occur during high-temperature aging and the OCV distribution becomes large.

[0066] In one embodiment of the present invention, the weight ratio of the sultone compound to the compound represented by Chemical Formula 1 (sultone compound: compound represented by Chemical Formula 1) may be 1:9 to 9:1. Specifically, it may be 2:8 to 9:1, or may be 5:5 to 8:2. More specifically, it may be 7:3 to 8:2.

[0067] When the above range is satisfied, optimal film resistance can be obtained, and the OCV distribution after the battery activation process is improved sharply, so that the battery yield is also increased. On the contrary, when the proportion of the sultone compound is excessively high, the interfacial resistance becomes excessively large, and when the proportion of the sultone compound is excessively low, there is a problem that self-discharge becomes excessively large during high-temperature aging.

[0068] In one embodiment of the present invention, the weight ratio of the sultone compound and the LiPO2F2 (sultone compound: LiPO2F2) may be 1:9 to 9:1. Specifically, it may be 2:8 to 8:2, or 2:8 to 5:5. More specifically, it may be 3:7 to 4:6.

[0069] When the above range is satisfied, optimal film resistance can be obtained, and the OCV distribution after the battery activation process is improved sharply, so that the battery yield is also increased.

[0070] One embodiment of the present invention provides an electrolyte for a lithium secondary battery, which includes a lithium salt; an organic solvent; and the above-described electrolyte additive.

[0071] As the lithium salt contained in the electrolyte, those commonly used in electrolytes for lithium secondary batteries may be used without limitation. For example, the lithium salt contains Li as a cation + and F as an anion - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3- 、(CF3)4PF2 - 、(CF3)5PF - 、(CF3)6P - 、CF3SO3 - 、C4F9SO3 - 、CF3CF2SO3 - 、(CF3SO2)2N - 、(FSO2)2N - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、CF3(CF2)7SO3 - 、CF3CO2 - 、CH3CO2 - 、SCN - 、および (CF3CF2SO2)2N - It may contain at least one selected from the group consisting of

[0072] In one embodiment of the present invention, the lithium salt may be one or more selected from the group consisting of LiPF6 and LiN(CF3SO2)2 (LiFSI).

[0073] The lithium salt may usually be appropriately changed within a usable range, but in order to obtain an optimal effect of forming a film for preventing corrosion of the electrode surface, it may be contained in the electrolytic solution at a total concentration of 0.8 M to 2.0 M.

[0074] The organic solvent contained in the electrolytic solution may include any one selected from the group consisting of ether solvents, ester solvents, and amide solvents, or a mixture of two or more selected from the group. The organic solvent is not limited thereto, and those commonly used in electrolytic solutions for lithium secondary batteries may be used without limitation.

[0075] Among the organic solvents, as the ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more thereof may be used, but is not limited thereto.

[0076] In addition, the ester-based solvent may contain at least one or more compounds selected from the group consisting of cyclic carbonate compounds, linear carbonate compounds, linear ester compounds, and cyclic ester compounds.

[0077] Among them, specific examples of the cyclic carbonate compound include any one 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, vinylene carbonate, and fluoroethylene carbonate (FEC), or a mixture of two or more thereof.

[0078] In addition, specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, or a mixture of two or more thereof, and the like may typically be used, but are not limited thereto.

[0079] Specific examples of the linear ester compound include, but are not limited to, any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more thereof.

[0080] Specific examples of the cyclic ester compound include, but are not limited to, any one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof.

[0081] At this time, among the ester solvents, cyclic carbonate compounds can be preferably used as high-viscosity organic solvents because they have a high dielectric constant and can well dissociate lithium salts in the electrolyte. When a linear carbonate compound with low viscosity and low dielectric constant such as dimethyl carbonate and diethyl carbonate is mixed with such a cyclic carbonate compound in a suitable ratio and used, an electrolyte with high electrical conductivity can be produced, so it can be more preferably used.

[0082] In one embodiment of the present invention, the organic solvent may contain a carbonate compound.

[0083] In one embodiment of the present invention, the organic solvent may be a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0084] In one embodiment of the present invention, the electrolyte for the lithium secondary battery may further contain an additional additive as required. Specifically, the additional additive is not particularly limited as long as it is an additive for forming a stable SEI film that can form a stable film on the surfaces of the positive electrode and the negative electrode.

[0085] Specifically, it may further contain one or more additives selected from the group consisting of a carbonate compound substituted with a halogen group, a nitrile compound, a cyclic carbonate compound, a phosphate compound, a borate compound, a cyclic sulfite, an acyclic sulfone, and a lithium salt compound.

[0086] Specifically, the carbonate compound substituted with the halogen group may be fluoroethylene carbonate (FEC), and may be contained in an amount of 5 parts by weight or less based on 100 parts by weight of the electrolyte, and specifically may be contained in an amount of 0.1 part by weight to 5 parts by weight. When the content of the carbonate compound substituted with the halogen group exceeds 5 parts by weight, the swelling performance of the cell may deteriorate.

[0087] In addition, the nitrile compound includes at least one or more compounds 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, and 4-fluorophenylacetonitrile.

[0088] At this time, when the nitrile compound is used together with the above-mentioned additives, effects such as improvement of high-temperature characteristics can be expected due to the stabilization of the positive / negative electrode coatings. That is, it can serve as a complementary agent when forming the negative electrode SEI coating, play a role in suppressing the decomposition of the solvent in the electrolyte, and play a role in improving the mobility of lithium ions. Such a nitrile compound may be contained in an amount of 5 parts by weight or less based on 100 parts by weight of the non-aqueous electrolyte, and specifically may be contained in an amount of 0.1 part by weight to 2 parts by weight. When the total content of the nitrile compound in the non-aqueous electrolyte exceeds the above range, the resistance increases due to the increase in the coating formed on the surface of the electrode, and the performance of the battery may deteriorate.

[0089] The cyclic carbonate-based compound forms a stable SEI film mainly on the surface of the negative electrode during activation of the battery, thereby improving the durability of the battery. Examples of such cyclic carbonate-based compounds include vinylene carbonate (VC) or vinyl ethylene carbonate, and may be contained in an amount of 5 parts by weight or less based on 100 parts by weight of the non-aqueous electrolyte, specifically 0.1 to 5 parts by weight. If the content of the cyclic carbonate-based compound in the non-aqueous electrolyte exceeds 5 parts by weight, the swelling suppression performance and initial resistance of the cell may be deteriorated.

[0090] The phosphate-based compound is PF6 - It stabilizes the above and is useful for forming the positive and negative electrode coatings, thereby improving the durability of the battery. Such phosphate-based compounds include one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate (LiDFOP), lithium difluorophosphate (LiDFP, LiPO2F2,), tetramethyltrimethylsilylphosphate (LiTFOP), trimethylsilylphosphite (TMSPi), tris(2,2,2-trifluoroethyl)phosphate (TFEPa), and tris(trifluoroethyl)phosphite (TFEPi), and may be contained in an amount of 3 parts by weight or less based on 100 parts by weight of the nonaqueous electrolyte. Specifically, it may be contained in an amount of 0.01 parts by weight or more and 3 parts by weight or less.

[0091] The borate compound can promote the separation of the ion pair of the lithium salt, improve the mobility of lithium ions, reduce the interfacial resistance of the SEI film, and dissociate substances such as LiF that are generated during the battery reaction and are not easily separated, thereby solving problems such as the generation of hydrofluoric acid gas. Examples of such borate compounds include lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2), lithium oxalato difluoroborate, or tetramethyl trimethylsilyl borate (TMSB), and it may be contained in an amount of 3 parts by weight or less based on 100 parts by weight of the non-aqueous electrolyte. Specifically, it may be contained in an amount of 0.01 part by weight or more and 3 parts by weight or less.

[0092] In addition, the lithium salt compound is a compound different from the lithium salt contained in the non-aqueous electrolyte, and examples include one or more compounds selected from the group consisting of LiODFB and LiBF4, and it may be contained in an amount of 3 parts by weight or less based on 100 parts by weight of the non-aqueous electrolyte. Specifically, it may be contained in an amount of 0.01 part by weight or more and 3 parts by weight or less.

[0093] The additives for SEI film formation can be used by mixing two or more kinds, and may be contained in an amount of 10 parts by weight or less, specifically 0.01 part by weight to 10 parts by weight, preferably 0.1 part by weight to 5.0 parts by weight, based on 100 parts by weight of the electrolyte.

[0094] When the content of the additional additive satisfies the above range, a more excellent film formation effect can be achieved. When it is 10 parts by weight or less, it is possible to prevent a decrease in the capacity of the battery due to side reactions of excess non-aqueous electrolyte additives, an increase in the viscosity of the electrolyte, and thereby an increase in resistance and a decrease in ion conductivity. If the content of the additional additive exceeds 10 parts by weight, side reactions in the electrolyte may occur excessively during charging and discharging of the battery. In particular, when the additive for SEI film formation is added in excess, it cannot be decomposed sufficiently and may exist in an unreacted or precipitated state in the electrolyte at room temperature. For this reason, the resistance increases and the life characteristics of the secondary battery may deteriorate.

[0095] In one embodiment of the present invention, the electrolyte for the lithium secondary battery may further contain vinylene carbonate (VC), fluoroethylene carbonate (FEC), and succinonitrile (SN).

[0096] In one embodiment of the present invention, the sultone compound is contained in an amount of 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the electrolyte. Specifically, it may be contained in an amount of 0.1 parts by weight to 2 parts by weight, 0.1 parts by weight to 1.5 parts by weight, or 0.2 parts by weight to 1 part by weight. More specifically, it may be contained in an amount of 0.4 parts by weight to 0.6 parts by weight, or 0.5 parts by weight. If the content of the S-containing additive such as the sultone compound is more than the above range, the interfacial resistance becomes excessively large, and if it is less than the above range, there is a problem that sufficient interfacial resistance cannot be obtained.

[0097] In one embodiment of the present invention, the LiPO2F2 is contained in an amount of 0.1 parts by weight to 2 parts by weight based on 100 parts by weight of the electrolyte. Specifically, it may be contained in an amount of 0.3 parts by weight to 2 parts by weight, or 0.5 parts by weight to 2 parts by weight. More specifically, it may be contained in an amount of 0.5 parts by weight to 1.2 parts by weight, 1 part by weight to 1.2 parts by weight, or 1 part by weight. If the content of LiPO2F2 is less than the above range, it is difficult to sufficiently reduce the interfacial resistance, and if it is more than the above range, there is a problem that it may not be well dissolved even if it is contained in the electrolyte, so it is difficult to exhibit the effect itself.

[0098] In one embodiment of the present invention, the compound represented by Chemical Formula 1 is contained in an amount of 0.01 parts by weight to 3 parts by weight based on 100 parts by weight of the electrolyte. Specifically, it may be contained in an amount of 0.05 parts by weight to 1 part by weight, or 0.05 parts by weight to 0.5 part by weight. More specifically, it may be contained in an amount of 0.1 parts by weight to 0.5 parts by weight, or 0.2 parts by weight. If the content of the compound represented by Chemical Formula 1 is less than the above range, the effect of suppressing excessive film formation of the sultone compound cannot be obtained, and if it is more than the above range, a large amount of reduction decomposition gas is generated during the first charge, increasing the internal pressure of the battery.

[0099] Therefore, when the sultone compound, LiPO2F2, and the compound represented by Chemical Formula 1 all satisfy the content ranges, optimal film resistance can be obtained, and the OCV distribution after the battery activation process is improved sharply, so that the battery yield can be improved.

[0100] One embodiment of the present invention provides a lithium secondary battery including the electrolyte for a lithium secondary battery.

[0101] Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the electrolyte includes the electrolyte for a lithium secondary battery of the present invention.

[0102] In addition, the lithium secondary battery of the present invention can be manufactured by injecting the non-aqueous electrolyte of the present invention into an electrode structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. At this time, any of the positive electrode, the negative electrode, and the separator forming the electrode structure may be used as long as they are commonly used in the manufacture of lithium secondary batteries.

[0103] In one embodiment of the present invention, the lithium secondary battery including the electrolyte for a lithium secondary battery may include a mixed SEI film of P-based, carbonate-based, and S-based, which can be confirmed by elemental analysis using XPS.

[0104] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0105] The positive electrode can be formed by coating a positive electrode slurry including a positive electrode active material, a positive electrode binder, a positive electrode conductive material, and a solvent on a positive electrode current collector, followed by drying and rolling.

[0106] In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity. 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. Further, the positive electrode current collector may usually have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesive force of the positive electrode active material. For example, it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabric bodies, etc.

[0107] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; chemical formula Li 1+c1 Mn 2-c1 O4 (0 ≦ c1 ≦ 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-c2 M c2 O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01 ≦ c2 ≦ 0.3); Ni-site type lithium nickel oxide represented by chemical formula LiMn 2-c3 M c3 O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01 ≦ c3 ≦ 0.1), or lithium manganese composite oxide represented by Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); or LiMn2O4 in which a part of the chemical formula of Li is substituted with an alkaline earth metal ion, etc. may be mentioned, but not limited thereto. The positive electrode may be Li-metal.

[0108] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0109] At this time, the positive electrode conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without particular limitation as long as it does not cause a chemical change and has electron conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more thereof may be used.

[0110] Also, the positive electrode binder serves to improve the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene polymer (EPDM), sulfonated - EPDM, styrene - butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these alone or a mixture of two or more thereof may be used.

[0111] The solvent may contain an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that results in a preferred viscosity when the positive electrode active material, and optionally a binder, a conductive material, etc. are included. For example, it may be included such that the solid content concentration in the slurry containing the positive electrode active material, and optionally a binder and a conductive material, is 50% to 95% by weight, preferably 70% to 90% by weight.

[0112] The negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector and containing the negative electrode active material.

[0113] The negative electrode can be formed by coating a negative electrode slurry containing a negative electrode active material, a negative electrode binder, a negative electrode conductive material, a solvent, etc. on a negative electrode current collector, and then drying and rolling.

[0114] The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and has high conductivity. 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., an aluminum-cadmium alloy, etc. may be used. Also, similar to the positive electrode current collector, fine irregularities may 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, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0115] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation may be used. Specific examples include carbon-based active materials, silicon-based active materials, metal-based active materials capable of alloying with lithium; and a single substance selected from the group consisting of lithium-containing nitrides or a mixture of two or more of these.

[0116] As typical examples of the carbon-based active material, natural graphite, artificial graphite, expanded graphite, carbon fiber, graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, etc. are representative, and any material commonly used for carbon materials for lithium secondary batteries may be used without limitation.

[0117] As typical examples of the silicon-based active material, silicon, an alloy of silicon, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiO v (0.5 ≦ v ≦ 1.2), and one or more selected from the group consisting of LiSiO may be mentioned.

[0118] As typical examples of the metal-based active material, it may be a compound containing any one or two or more metal elements selected from the group consisting of Al, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, Ti, Sb, Ga, Mn, Fe, Co, Ni, Cu, Sr, and Ba, etc. These metal compounds may be used in any form such as a single substance, an alloy, an oxide (such as TiO2, SnO2), a nitride, a sulfide, a boride, an alloy with lithium, etc., but a single substance, an alloy, an oxide, and an alloy with lithium can achieve a high capacity.

[0119] At this time, when a silicon-based active material or a negative electrode containing both a silicon-based active material and a carbon-based active material is used as the negative electrode active material, a lithium secondary battery with further improved various performances such as cycle life characteristics can be manufactured. That is, in the case of a silicon-based active material, since the volume change is large during charge and discharge, the stability of the SEI is extremely reduced. On the other hand, when using a non-aqueous electrolyte containing the additive of the present invention, since the content of LiF in the non-aqueous electrolyte increases, a rich SEI film capable of compensating for the disadvantages of the silicon-based active material can be formed, so the effect of improving the life of the secondary battery using the silicon-based negative electrode active material is even greater.

[0120] The negative electrode active material layer may contain a negative electrode conductive material and a negative electrode binder together with the aforementioned negative electrode active material.

[0121] The negative electrode binder is a component that aids in the bonding between the conductive material, the active material, and the current collector, and is usually 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 (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0122] The negative electrode 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 slurry. Such a conductive material is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0123] The solvent may contain water or an organic solvent such as NMP or alcohol, and may be used in an amount that results in a preferable viscosity when containing the negative electrode active material and optionally a binder and a conductive material. For example, it may be contained such that the solid content concentration in the slurry containing the negative electrode active material and optionally a binder and a conductive material is 50 to 95% by weight, preferably 70 to 90% by weight.

[0124] As the separator, it 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 secondary battery can be used without particular limitation, and it is particularly preferably low in resistance to the ion migration of the electrolyte and excellent in the ability to hold the electrolyte. Specifically, 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. Also, a normal porous non-woven fabric, for example, a non-woven 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 selectively used as a single-layer or multi-layer structure.

[0125] In another embodiment of the present invention, the lithium secondary battery may be a cylindrical battery. Specifically, the cylindrical battery may be a 18650 battery or a 21700 battery.

[0126] According to still another embodiment of the present invention, there are provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same. Since the battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and cycle characteristics, they can be used as a power source for medium and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

Examples

[0127] Hereinafter, examples will be given to specifically describe this specification in detail. However, the examples according to this specification may be deformed into various different forms, and the scope of this application should not be construed as being limited to the examples described below. The examples of this application are provided to more fully explain this specification to those with average knowledge in the industry.

[0128] Example 1 1) Preparation of electrolyte for lithium secondary battery To 93.8 g of a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) mixed in a volume ratio of 20:20:60) in which LiPF6 was dissolved to be 1.5 M, 0.5 g of 1,3-propanesultone (PS), 0.2 g of methyl prop-2-yn-1-yl carbonate (Ky01, Syntechem), 1 g of LiPO2F2, 2 g of vinylene carbonate (VC), 2 g of fluoroethylene carbonate (FEC), and 0.5 g of succinonitrile (SN) were added to produce a non-aqueous electrolyte.

[0129] 2) Preparation of lithium secondary battery In the solvent N-methyl-2-pyrrolidone (NMP), as a positive electrode active material (Li(Ni 0.5 Mn 0.3 Co 0.2 )O2), a conductive material (carbon black), and a binder (polyvinylidene fluoride; PVDF) were added in a weight ratio of 95.05:2.15:2.80 to produce a positive electrode slurry. After the positive electrode slurry was applied and dried on an aluminum (Al) thin film which was a positive electrode current collector with a thickness of about 15 μm, it was rolled by a roll press to produce a positive electrode.

[0130] To a solvent of H2O, a negative electrode active material (graphite), a conductive material (carbon black), a binder (styrene butadiene rubber; SBR), and CMC (carboxymethyl cellulose) were added at a weight ratio of 97.0:1.2:0.8:1.0 to produce a negative electrode slurry. After the negative electrode slurry was coated and dried on a copper (Cu) thin film, which is a negative electrode current collector with a thickness of 15 μm, it was rolled by a roll press to produce a negative electrode.

[0131] The positive electrode, the negative electrode, and a separator made of Al2O3 coating PE were sequentially laminated to produce an electrode assembly.

[0132] After the electrode assembly was placed inside a case, an electrolytic solution was injected into the case to produce a lithium secondary battery.

[0133] Example 2 A lithium secondary battery was produced in the same manner as in Example 1, except that 0.05 g of methyl prop-2-yn-1-yl carbonate was added to 93.95 g of a non-aqueous organic solvent.

[0134] Example 3 A lithium secondary battery was produced in the same manner as in Example 1, except that 0.5 g of methyl prop-2-yn-1-yl carbonate was added to 93.5 g of a non-aqueous organic solvent.

[0135] Example 4 A lithium secondary battery was produced in the same manner as in Example 1, except that 0.2 g of 1,3-propanesultone was added to 94.1 g of a non-aqueous organic solvent.

[0136] Example 5 A lithium secondary battery was produced in the same manner as in Example 1, except that 1 g of 1,3-propanesultone was added to 93.3 g of a non-aqueous organic solvent.

[0137] Example 6 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of LiPO2F2 was added to 94.3 g of a non-aqueous organic solvent.

[0138] Example 7 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 1.2 g of LiPO2F2 was added to 93.6 g of a non-aqueous organic solvent.

[0139] Example 8 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 0.5 g of 1-propene-1,3-sultone (PRS) was added to 93.8 g of a non-aqueous organic solvent instead of 1,3-propanesultone.

[0140] Example 9 A lithium secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous organic solvent in which LiPF6 was dissolved to be 0.8 M and LiFSI was 0.7 M was used instead of 1.5 M LiPF6.

[0141] Comparative Example 1 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 2 g of vinylene carbonate (VC) and 2 g of fluoroethylene carbonate (FEC) were added to 96 g of a non-aqueous organic solvent (ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) mixed at a volume ratio of 20:20:60) in which LiPF6 was dissolved to be 1.5 M to produce a non-aqueous electrolyte.

[0142] Comparative Example 2 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that 1 g of LiPO2F2 was further added to 95 g of a non-aqueous organic solvent.

[0143] Comparative Example 3 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that 1 g of LiPO2F2 and 0.5 g of succinonitrile were further added to 94.5 g of a non-aqueous organic solvent.

[0144] Comparative Example 4 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that 0.2 g of methylprop-2-yn-1-yl carbonate, 1 g of LiPO2F2, and 0.5 g of succinonitrile were further added to 94.3 g of the non-aqueous organic solvent.

[0145] Comparative Example 5 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that 0.5 g of 1,3-propane sultone, 1 g of LiPO2F2, and 0.5 g of succinonitrile were further added to 94 g of the non-aqueous organic solvent.

[0146] Comparative Example 6 A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that 0.5 g of 1,3-propane sultone, 0.2 g of methylprop-2-yn-1-yl carbonate, and 0.5 g of succinonitrile were further added to 94.8 g of the non-aqueous organic solvent.

[0147] The compositions of the electrolytes of the secondary batteries manufactured in the above Examples and Comparative Examples are as shown in Table 1 below.

[0148]

Table 1

[0149] Experimental Example: Evaluation of Lithium Secondary Battery <Measurement of OCV Distribution> The lithium secondary batteries manufactured in Examples 1 to 9 and Comparative Examples 1 to 6 were each precharged at 0.3C to SOC 0.8%, and then aged at 60°C for 1 day. Thereafter, after primary charging (0.2C, SOC 80%), high temperature (60°C, 24 hr) and normal temperature (12 hr) aging were performed, and then CC discharge (2 steps, 1.5C 2.5V / 0.2C 2.5V) was performed. Finally, an activation process was performed through the process of shipping charge (CCCV 1C, 3.61V 100mA cut-off).

[0150] After the activation process, finally, after storing at normal temperature for 5 days, the open circuit voltage (OCV) was measured at 1000 Hz, R range 100 mΩ, Z speed slow, V speed fast conditions through a battery impedance meter device manufactured by HIOKI, and it is shown in Table 2 below.

[0151] Figures 1 to 9 respectively show the OCV distributions of Examples 1 to 9, and Figures 10 to 15 respectively show the OCV distributions of Comparative Examples 1 to 6.

[0152]

Table 2

[0153] It can be confirmed that the battery using the electrolyte additive of the present invention shows a very sharp shape in the OCV distribution after the completion of the activation process.

[0154] Specifically, referring to the OCV distributions of Examples 1 to 9, it was confirmed that the value of 3 standard deviations (3σ) was as low as 0 mV to 2 mV. It was also confirmed that the OCV distribution showed a very sharp shape in the graphs showing the OCV distributions of the examples in FIGS. 1 to 9.

[0155] On the other hand, referring to the OCV distributions of Comparative Examples 1 to 6 that do not have the configuration of the electrolyte additive of the present invention, it was confirmed that the value of 3 standard deviations (3σ) was as high as 3 mV to 6 mV. This means that the voltage values corresponding to the OCV occurrence frequency are more widely distributed than in Examples 1 to 9. It was also confirmed that in the graphs showing the OCV distributions of the comparative examples in FIGS. 10 to 15, the OCV voltage values are widely distributed or present as double peaks, and there is a high possibility of being determined as defective.

[0156] Therefore, the battery using the electrolyte additive according to one embodiment of the present invention shows a very sharp shape in the OCV distribution after the completion of the activation process, and thus can contribute to an improvement in the battery yield.

Claims

1. A lithium salt; an organic solvent; and, Sulton-based compound; LiPO ２ F ２ ; and a compound represented by the following Chemical Formula 1; an electrolyte for a lithium secondary battery having an electrolyte additive containing [Chemical Formula 1] 【Chemical 1】 In the above Chemical Formula 1, R1 is hydrogen; a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms; or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, L1 is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, The compound represented by the above Chemical Formula 1 is contained in an amount of 0.05 parts by weight to 0.5 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery, An electrolyte for a lithium secondary battery.

2. The electrolyte for a lithium secondary battery according to Claim 1, wherein the R1 is an alkyl group having 1 to 10 carbon atoms.

3. The electrolyte for a lithium secondary battery according to Claim 1, wherein the L1 is an alkylene group having 1 to 5 carbon atoms.

4. The electrolyte for a lithium secondary battery according to Claim 1, wherein the weight ratio of the sultone compound and the compound represented by the above Chemical Formula 1 (sultone compound: compound represented by Chemical Formula 1) is contained in a ratio of 5:5 to 8:

2.

5. The sultone compound is one or more selected from the group consisting of 1,3-propanesultone; and 1-propene 1,3-sultone, The compound represented by the above Chemical Formula 1 is methyl prop-2-yn-1-yl carbonate, and the electrolyte for a lithium secondary battery according to Claim 1.

6. The electrolyte for a lithium secondary battery according to Claim 1, wherein the sultone compound is contained in an amount of 0.1 parts by weight to 5 parts by weight based on 100 parts by weight of the electrolyte for a lithium secondary battery.

7. The aforementioned LiPO ２ F ２ is contained in an amount of 0.1 part by weight to 2 parts by weight based on 100 parts by weight of the electrolyte for the lithium secondary battery according to claim 1.

8. The lithium salt contains Li as a cation ＋ and As anions, F － , Cl － , Br － , I － , NO ３ － , N(CN) ２ － , BF ４ － , ClO ４ － , AlO ４ － , AlCl ４ － , PF ６ － , SbF ６ － , AsF ６ － , BF ２ C ２ O ４ － , BCO ４ O ８ － , (CF ３ ) ２ , PF ４ － , (CF ３ ) ３ , PF ３ － , (CF ３ ) ４ , PF ２ － , (CF ３ ) ５ , PF － , (CF ３ ) ６ , P － , CF ３ , SO ３ － , C ４ , F ９ , SO ３ － , CF ３ , CF ２ , SO ３ － , (CF ３ , SO ２ ) ２ , N － , (FSO ２ ) ２ , N － , CF ３ CF ２ (CF ３ ) ２ CO － 、(CF ３ SO ２ ) ２ CH － 、CF ３ (CF ２ ) ７ SO ３ － 、CF ３ CO ２ － 、CH ３ CO ２ － 、SCN － 、and (CF ３ CF ２ SO ２ ) ２ N － The electrolyte for a lithium secondary battery according to claim 1, comprising one or more selected from the group consisting of

9. The electrolyte for a lithium secondary battery according to Claim 1, wherein the organic solvent contains one selected from the group consisting of an ether-based solvent, an ester-based solvent, and an amide-based solvent or a mixture of two or more selected from the above group.

10. The electrolyte for a lithium secondary battery according to Claim 1, further contains one or more additives selected from the group consisting of a carbonate-based compound substituted with a halogen group, a nitrile-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, a cyclic sulfite, an acyclic sulfone, and a lithium salt-based compound.

11. A lithium secondary battery containing the electrolyte for a lithium secondary battery according to any one of Claims 1 to 10.

12. The lithium secondary battery according to claim 11, which is a cylindrical battery.

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