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

Abstract

A non-aqueous electrolyte for a lithium secondary battery is provided, which includes a lithium salt, an organic solvent, and a phosphoric acid additive having a specific structure. By adding the phosphoric acid additive according to one embodiment of the present invention to the electrolyte, the high temperature stability of the lithium secondary battery can be significantly improved.

Description

[Technical field]

[0001] The present invention relates to a non-aqueous electrolyte for a secondary battery, which can improve high-temperature storage characteristics and life characteristics of a lithium secondary battery, and a lithium secondary battery including the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0155283 filed on November 12, 2021 and Korean Patent Application No. 10-2022-0144880 filed on November 3, 2022, and all contents disclosed in the documents of said Korean patent applications are incorporated as part of this specification. [Background technology]

[0003] Recently, the application areas of lithium secondary batteries have been rapidly expanded to include power supply for electronic devices such as electrical, electronic, communication, and computer devices, as well as power storage supply for large-area devices such as automobiles and power storage devices, and thus there is an increasing demand for secondary batteries with high capacity, high output, and high stability.

[0004] Lithium secondary batteries are generally manufactured by coating a positive electrode active material made of lithium-containing transition metal oxide or a negative electrode active material made of carbon or silicon capable of absorbing and releasing lithium ions with a binder and a conductive material on a positive electrode collector and a negative electrode collector, respectively, to manufacture a positive electrode and a negative electrode, which are then laminated on both sides of a separator to form an electrode collector of a predetermined shape, and then inserting the electrode collector and non-aqueous electrolyte into a battery case. In order to ensure the performance of the battery, formation and aging processes are almost always required.

[0005] The formation process is a step in which the secondary battery is activated by repeatedly charging and discharging after the battery is assembled. During the charging process, lithium ions released from the lithium-containing transition metal oxide used in the positive electrode move to and are inserted into the carbon material negative electrode active material used in the negative electrode. At this time, the highly reactive lithium ions react with the electrolyte to form Li 2 CO3 , Li 2 Compounds such as O, LiOH, and LiF are generated, and these compounds form a solid electrolyte interface (SEI) layer on the surface of the electrode. The SEI layer closely affects the life and capacity maintenance, so the formation of the SEI layer is an important factor.

[0006] Recently, high capacity, high output, and long life characteristics have become important, especially for lithium secondary batteries for automobiles. In order to increase capacity, positive electrode active materials with high energy density but low stability are used, so it is necessary to form an active material-electrolyte interface that can protect the surface of the positive electrode active material and stabilize the positive electrode active material, while problems such as side reactions caused by the surface species of the negative electrode being decomposed by the electrolyte have been reported for the negative electrode.

[0007] Specifically, lithium-ion batteries currently often use high-voltage and high-content nickel positive electrodes to ensure energy density, and as the battery voltage increases, electrochemical side reactions on the surface of the positive electrode increase. In the case of nickel-cobalt-manganese (NCM) positive electrodes, as the nickel content increases, structural instability increases and electrolyte decomposition can be accelerated. At this time, gas is generated as the solvent decomposes, resistance increases, and HF is generated by salt decomposition, which can accelerate the elution of transition metals from the positive electrode active material, which is a metal oxide. In addition, the SEI layer formed on the surface of the active material can be destroyed, causing problems such as increased battery resistance and reduced lifespan, and when stored at high temperatures, HF and PF generated in the electrolyte can be released. 5 As a result, the positive electrode structure and the SEI layer may gradually collapse, causing additional side reactions at the electrode. Therefore, in order to solve the above problems, research into forming a robust SEI layer capable of suppressing side reactions during high-temperature storage has been ongoing in the art, including research into additives in the electrolyte. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 10-2011-0116019 [Patent Document 2] Korean Patent Publication No. 10-2015-0089712 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the problems of the related art, and aims to provide an electrolyte for a lithium secondary battery, which contains a phosphoric acid-based additive having a specific structure and excellent conductivity, capable of forming a coating that can effectively suppress side reactions that inevitably occur on the surfaces of positive and negative electrodes in a lithium secondary battery, as an additive to a non-aqueous electrolyte for a lithium secondary battery, thereby improving the high-temperature storage characteristics and life characteristics of the lithium secondary battery containing the same.

[0010] Another object of the present invention is to provide a lithium secondary battery that contains the nonaqueous electrolyte solution for a lithium secondary battery, thereby enabling the formation of a coating on the surfaces of a positive electrode and a negative electrode, and thus significantly improving the durability of the battery, i.e., high-temperature storage characteristics and life characteristics. [Means for solving the problem]

[0011] To achieve the above object, the present invention provides a non-aqueous electrolyte for a lithium secondary battery, comprising a lithium salt, an organic solvent, and a phosphoric acid additive represented by the following Chemical Formula 1: [ka]

[0012] In the above Chemical Formula 1, The R is a functional group useful for forming a coating film, and is a chain or ring structure functional group containing one or more elements of H, C, N, O, F, P, S, and Si.

[0013] In addition, an embodiment of the present invention is a compound represented by the formula 1, wherein R is the same or different and each R is independently hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted mercapto, substituted or unsubstituted carbamoyl, substituted or unsubstituted C 1‐7 Alkyl, substituted or unsubstituted C 1‐7 Alkyl halides, substituted or unsubstituted C 2‐7 Alkenyl, substituted or unsubstituted C 2‐7 Alkynyl, substituted or unsubstituted C 1‐7 Alkoxy, substituted or unsubstituted C 1‐4 Alkoxy-C 1‐4 Alkoxy, substituted or unsubstituted C 6‐10 Aryl-C 1‐4 Alkoxy, substituted or unsubstituted C 2‐7 Alkenyloxy, substituted or unsubstituted C 2‐7 Alkynyloxy, substituted or unsubstituted C 3‐7 Cycloalkyl, substituted or unsubstituted C 3‐7 Cycloalkenyl, substituted or unsubstituted 3-7 membered heterocycloalkyl, substituted or unsubstituted C 3‐7 Cycloalkyloxy, substituted or unsubstituted C 3‐7 Cycloalkenyloxy, substituted or unsubstituted 3-7 membered heterocycloalkyloxy, substituted or unsubstituted C 6‐10 Aryl, substituted or unsubstituted 5-10 membered heteroaryl, substituted or unsubstituted C 6‐10 Aryloxy, substituted or unsubstituted 5-10 membered heteroaryloxy, substituted or unsubstituted mono- or di-C 1‐4 Alkylamino, substituted or unsubstituted mono- or di-C 6‐10 Arylamino, substituted or unsubstituted C 1‐4 Alkylcarbonylamino, substituted or unsubstituted C 1‐4 Alkylcarbonyl, substituted or unsubstituted C 1‐4 Alkoxycarbonyl, substituted or unsubstituted C 2‐4 Alkenyloxycarbonyl, and substituted or unsubstituted C2‐4 The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, the non-aqueous electrolyte solution being selected from the group consisting of alkynyloxycarbonyl.

[0014] In one embodiment of the present invention, in the formula 1, R is the same or different, and each R is independently hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted C 1‐4 Alkyl, substituted or unsubstituted C 1‐4 Alkyl halides, substituted or unsubstituted C 2‐4 Alkenyl, substituted or unsubstituted C 2‐4 Alkynyl, substituted or unsubstituted C 1‐4 Alkoxy, substituted or unsubstituted mono- or di-C 1‐4 Alkylamino, substituted or unsubstituted C 1‐4 Alkylcarbonyl and substituted or unsubstituted C 1‐4 The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, the non-aqueous electrolyte solution being selected from the group consisting of alkoxycarbonyls.

[0015] In one embodiment of the present invention, in the formula 1, the R's are the same or different and each R is independently hydrogen, halogen, substituted or unsubstituted C 1‐4 Alkyl, substituted or unsubstituted C 1‐4 Alkyl halides and substituted or unsubstituted C 2‐4 The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, wherein the non-aqueous electrolyte is selected from the group consisting of alkenyl.

[0016] An embodiment of the present invention provides a non-aqueous electrolyte for a lithium secondary battery, in which the phosphoric acid-based additive is contained in an amount of 0.01 wt % to 10 wt % based on the total weight of the electrolyte.

[0017] In an embodiment of the present invention, the lithium salt is LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiB 10 Cl 10 , LiAlCl 4 , LiAlO4 , LiPF 6 , LiCF 3 SO 3 , LiCH 3 CO 2 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiCH 3 SO 3 , LiSO 3 F, LiN(SO 2 F) 2 , LiN(SO 2 CF 2 CF 3 ) 2 and LiN(SO 2 CF 3 ) 2 The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, which is selected from the group consisting of:

[0018] An embodiment of the present invention provides a nonaqueous electrolyte solution for a lithium secondary battery, wherein the concentration of the lithium salt is 0.1M to 3M.

[0019] An embodiment of the present invention provides a nonaqueous electrolyte for a lithium secondary battery, wherein the organic solvent includes at least one selected from the group consisting of ethers, esters, amides, linear carbonates, and cyclic carbonates.

[0020] An embodiment of the present invention provides a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution for the lithium secondary battery.

[0021] An embodiment of the present invention provides a lithium secondary battery, wherein the positive electrode has a layered structure based on a positive electrode active material and contains a lithium transition metal oxide in which the nickel content of all transition metals is 60 atm% or more. Effect of the Invention

[0022] The non-aqueous electrolyte for lithium secondary batteries according to the present invention contains a phosphoric acid-based additive having a specific structure, and not only suppresses the decomposition reaction of the non-aqueous electrolyte itself, but also forms a coating on the surfaces of the positive and negative electrodes, thereby effectively suppressing side reactions that inevitably occur on the surfaces of the positive and negative electrodes in lithium secondary batteries.

[0023] As a result, the durability, i.e., high-temperature storage characteristics and life characteristics, of the lithium secondary battery containing the nonaqueous electrolyte solution for lithium secondary batteries can be improved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The embodiments provided by the present invention can all be achieved by the following description. The following description should be understood as describing preferred embodiments of the present invention, and it should be understood that the present invention is not necessarily limited thereto.

[0025] As used herein, the term "C n1‐n2 " means that the functional group has n1 to n2 carbon atoms.

[0026] The term "alkyl" as used herein means a straight or branched chain saturated hydrocarbon containing one radical, which radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "alkyl" include, but are not necessarily limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl, and hexyl.

[0027] The term "alkylene" as used herein means a linear or branched saturated hydrocarbon containing two radicals, each of which determines a bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "alkylene" include, but are not necessarily limited to, methylene and ethylene.

[0028] The term "alkenyl" as used herein includes one radical and means a straight or branched chain hydrocarbon having one or more carbon-carbon double bonds, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "alkenyl" include, but are not necessarily limited to, ethenyl and propenyl.

[0029] The term "alkynyl" as used herein includes one radical and means a straight or branched chain hydrocarbon having one or more carbon-carbon triple bonds, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "alkynyl" include, but are not limited to, acetylenyl and 1-propynyl.

[0030] The term "halogen" as used herein means fluorine (F), chlorine (Cl), bromine (Br) or iodine (I).

[0031] As used herein, the term "halogenated alkyl" refers to an alkyl group in which one or more hydrogens have been replaced with a halogen.

[0032] The term "cycloalkyl" as used herein includes one radical and means a saturated hydrocarbon having one or more rings, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "cycloalkyl" include, but are not limited to, cyclopentyl, cyclohexyl, and cycloheptyl.

[0033] The term "cycloalkenyl" as used herein means a hydrocarbon having one or more rings and one or more carbon-carbon double bonds within the ring, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "cycloalkenyl" include, but are not necessarily limited to, cyclopentenyl, cyclohexenyl, and cycloheptenyl.

[0034] As used herein, the term "n 1 -n2 "N" is the sum of the number of carbon atoms and the number of hetero elements. 1 ~n 2 Although a hetero element broadly means an element other than carbon, in this specification, the term "n 1 -n 2 "Membered" is used before a cyclic functional group to refer to the number of elements that make up the ring.

[0035] The term "heterocycloalkyl" as used herein means a saturated hydrocarbon having one or more rings containing one radical and having one or more heteroatoms in the ring, and one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. The heteroatom can form a ring, and examples thereof include O, N, and S. Examples of the term "heterocycloalkyl" include, but are not limited to, piperidinyl and tetrahydropyranyl.

[0036] The term "aryl" as used herein includes one radical and means an aromatic ring system hydrocarbon having one or more rings, and the one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "aryl" include, but are not necessarily limited to, phenyl and naphthyl.

[0037] The term "arylene" used herein includes two radicals and means an aromatic ring-based hydrocarbon having one or more rings, and each of the two radicals determines a bonding position as a functional group, and the bonding position is not particularly limited. Examples of the term "arylene" include, but are not limited to, phenylene and naphthylene. The above-mentioned "alkylene" and "arylene" can be used in combination, for example, in the form of methylene-phenylene.

[0038] The term "heteroaryl" as used herein means an aromatic ring-type hydrocarbon having one or more rings containing one radical and one or more heteroatoms in the ring, and one radical determines the bonding position as a functional group, and the bonding position is not particularly limited. The heteroatom can form a ring, and examples thereof include O, N, S, and P. Examples of the term "heteroaryl" include, but are not limited to, pyrrolyl and furanyl.

[0039] As used herein, the term "alkoxy" refers to R a is alkyl as defined above; a Examples of the term "alkoxy" include, but are not limited to, methoxy, difluoromethoxy, trifluoromethoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, and t-butoxy.

[0040] As used herein, the term "alkoxy-alkoxy" refers to R a is alkylene and R b is alkyl as defined above; a -OR b Examples of the term "alkoxy-alkoxy" include, but are not necessarily limited to, methoxy-methoxy, methoxy-ethoxy, and ethoxy-ethoxy.

[0041] As used herein, the term "aryl-alkoxy" refers to R a is alkylene and R b is aryl as defined above -OR a -R b Examples of the term "aryl-alkoxy" include, but are not necessarily limited to, phenyl-methoxy and phenyl-ethoxy.

[0042] As used herein, the term "alkenyloxy" refers to R a is alkenyl as defined above -OR aExamples of the term "alkenyloxy" include, but are not limited to, ethenyloxy and propenyloxy.

[0043] As used herein, the term "alkynyloxy" refers to R a is alkynyl as defined above -OR a Examples of the term "alkynyloxy" include, but are not limited to, ethynyloxy and propynyloxy.

[0044] As used herein, the term "cycloalkyloxy" refers to R a is cycloalkyl as defined above -OR a Examples of the term "cycloalkyloxy" include, but are not limited to, cyclopentyloxy and cyclohexyloxy.

[0045] As used herein, the term "cycloalkenyloxy" refers to R a is cycloalkenyl as defined above -OR a Examples of the term "cycloalkenyloxy" include, but are not limited to, cyclopentenyloxy and cyclohexenyloxy.

[0046] As used herein, the term "heterocycloalkyloxy" refers to R a is heterocycloalkyl as defined above; a Examples of the term "heterocycloalkyloxy" include, but are not limited to, piperidinyloxy and tetrahydropyranyloxy.

[0047] As used herein, the term "aryloxy" refers to R a is aryl as defined above -OR a Examples of the term "aryloxy" include, but are not limited to, phenyloxy and naphthyloxy.

[0048] As used herein, the term "heteroaryloxy" refers to R a is heteroaryl as defined above; a Examples of the term "heteroaryloxy" include, but are not limited to, pyrrolyloxy and furanyloxy.

[0049] The term "mercapto" as used herein refers to a functional group in the form --SH.

[0050] As used herein, the term "hydroxy" refers to a functional group in the form --OH.

[0051] As used herein, the term "amino" means -NH 2 The amino group refers to a functional group having one or more hydrogen atoms substituted with the above-mentioned alkyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl. For example, if one hydrogen atom of the amino group is substituted with an alkyl group, the amino group is named as a mono-alkylamino group, and if two hydrogen atoms of the amino group are substituted with alkyl groups, the amino group is named as a di-alkylamino group.

[0052] As used herein, the term "carbonylamino" refers to R a is alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl as described above, and the like. a Here, hydrogen can also be substituted with alkyl, etc.

[0053] As used herein, the term "cyano" refers to a functional group of the form --CN.

[0054] As used herein, the term "carbamoyl" refers to -C(O)NH 2 In this case, one or more hydrogen atoms may be substituted with an alkyl group or the like.

[0055] As used herein, the term "nitro" means -NO 2 This refers to a functional group in the form of

[0056] As used herein, the term "carbonyl" refers to R a is alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, alkoxy, alkenyloxy, alkynyloxy, etc. as described above. a For example, R a When R is alkyl, it is also named "alkylcarbonyl" and a When R is alkoxy, it is also named "alkoxycarbonyl". a When R is alkenyloxy, it is also named "alkenyloxycarbonyl", a When it is alkynyloxy, it is also named "alkynyloxycarbonyl".

[0057] The term "substituted or unsubstituted" as used herein means that the functional group is present in a substituted or unsubstituted state, and substitution means that a hydrogen atom bonded to a carbon atom of a compound is replaced with another substituent, and the position of substitution is not limited to the position at which a hydrogen atom is replaced, i.e., a position at which a substituent can be substituted, and when two or more substituents are substituted, the two or more substituents may be the same or different.

[0058] The substituent may be any substituent commonly used in the art without any particular limitation. Examples of the substituent include halogen, hydroxy, cyano, nitro, amino, C 1‐4 Alkyl, C 1‐4 Alkyl halides, C 1‐4 Alkoxy, C 1‐4 Alkoxy-C 1‐4 Alkoxy, C 3‐7 Cycloalkyl, C 3‐7 Cycloalkenyl, C 3‐7 Cycloalkyloxy, 3-7 membered heterocycloalkyl, C 6‐10 Aryl, 5-10 membered heteroaryl, mono- or di-C 1‐4 Alkylamino, mono- or di-C 6‐10 Arylamino, carbonylamino, C1‐4 Alkyl carbonyl, C 1‐4 Alkoxycarbonyl, C 2‐4 Alkenyloxycarbonyl, and C 2‐4 Alkynyloxycarbonyl and the like.

[0059] In the present invention, when "no substituent is shown in the chemical formula or compound structure," it means that a hydrogen atom is bonded to a carbon atom. However, deuterium ( 2 H, Deuterium) is an isotope of hydrogen, so some of the hydrogen atoms may be deuterium.

[0060] The present invention provides a non-aqueous electrolyte for a lithium secondary battery, comprising a lithium salt, an organic solvent, and a phosphoric acid additive represented by the following Chemical Formula 1:

[0061] [ka]

[0062] In the above Chemical Formula 1, The R is a functional group useful for forming a coating film, and is a chain or ring structure functional group containing one or more elements of H, C, N, O, F, P, S, and Si.

[0063] In one embodiment of the present invention, in the formula 1, R is the same or different, and each R is independently hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted mercapto, substituted or unsubstituted carbamoyl, substituted or unsubstituted C 1‐7 Alkyl, substituted or unsubstituted C 1‐7 Alkyl halides, substituted or unsubstituted C 2‐7 Alkenyl, substituted or unsubstituted C 2‐7 Alkynyl, substituted or unsubstituted C 1‐7 Alkoxy, substituted or unsubstituted C 1‐4 Alkoxy-C 1‐4 Alkoxy, substituted or unsubstituted C 6‐10 Aryl-C1‐4 Alkoxy, substituted or unsubstituted C 2‐7 Alkenyloxy, substituted or unsubstituted C 2‐7 Alkynyloxy, substituted or unsubstituted C 3‐7 Cycloalkyl, substituted or unsubstituted C 3‐7 Cycloalkenyl, substituted or unsubstituted 3-7 membered heterocycloalkyl, substituted or unsubstituted C 3‐7 Cycloalkyloxy, substituted or unsubstituted C 3‐7 Cycloalkenyloxy, substituted or unsubstituted 3-7 membered heterocycloalkyloxy, substituted or unsubstituted C 6‐10 Aryl, substituted or unsubstituted 5-10 membered heteroaryl, substituted or unsubstituted C 6‐10 Aryloxy, substituted or unsubstituted 5-10 membered heteroaryloxy, substituted or unsubstituted mono- or di-C 1‐4 Alkylamino, substituted or unsubstituted mono- or di-C 6‐10 Arylamino, substituted or unsubstituted C 1‐4 Alkylcarbonylamino, substituted or unsubstituted C 1‐4 Alkylcarbonyl, substituted or unsubstituted C 1‐4 Alkoxycarbonyl, substituted or unsubstituted C 2‐4 Alkenyloxycarbonyl, and substituted or unsubstituted C 2‐4 It may be selected from the group consisting of alkynyloxycarbonyl.

[0064] In another embodiment of the present invention, in the formula 1, R is the same or different and each R is independently selected from hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted C 1‐4 Alkyl, substituted or unsubstituted C 1‐4 Alkyl halides, substituted or unsubstituted C 2‐4 Alkenyl, substituted or unsubstituted C 2‐4 Alkynyl, substituted or unsubstituted C 1‐4 Alkoxy, substituted or unsubstituted mono- or di-C 1‐4Alkylamino, substituted or unsubstituted C 1‐4 Alkylcarbonyl and substituted or unsubstituted C 1‐4 It may be selected from the group consisting of alkoxycarbonyl.

[0065] In another embodiment of the present invention, in Formula 1, R may be the same or different and each R is independently hydrogen, halogen, substituted or unsubstituted C 1‐4 Alkyl, substituted or unsubstituted C 1‐4 Alkyl halides and substituted or unsubstituted C 2‐4 It may be selected from the group consisting of alkenyl.

[0066] In an embodiment of the present invention, the phosphoric acid additive may be included in an amount of 0.01 wt% to 10 wt% based on the total weight of the electrolyte. Specifically, the phosphoric acid additive may be included in an amount of 0.01 wt% or more, 0.05 wt% or more, 0.1 wt% or more, 0.5 wt% or more, 1 wt% or more, 2 wt% or more, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less based on the total weight of the electrolyte, or may be 0.01 wt% to 10 wt%, 0.1 wt% to 5 wt%, 0.5 wt% to 3 wt%, or 1 wt% to 3 wt%. If the content of the phosphoric acid additive is less than the above range, the effect of the additive is not observed, such as suppressing swelling of the battery during high temperature storage or long-term battery operation, or only slightly improving the capacity retention rate, and the effect of improving the resistance increase rate of the lithium secondary battery is negligible, whereas if the content of the phosphoric acid additive exceeds the above range, there is a problem that the resistance increases excessively, causing rapid deterioration of the lifespan, and thus deteriorating the characteristics of the lithium secondary battery. Therefore, it is preferable that the content of the phosphoric acid additive satisfies the above range.

[0067] In one embodiment of the present invention, the non-aqueous electrolyte for a lithium secondary battery is lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiB(C 2 O4 ) 2 , LiBOB), Lithium borofluoride (LiBF 4 ), lithium difluoro(oxalato)borate (LiDFOP), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium difluorophosphate (LiPO 2 F 2 The composition may further include an additive selected from the group consisting of ethylene sultone, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, ethylene sulfate, propylene sulfite, diallyl sulfonate, ethane sultone, propane sultone (PS), butane sultone, ethene sultone, butene sultone, and propene sultone (PRS).

[0068] In one embodiment of the present invention, the non-aqueous electrolyte for a lithium secondary battery may contain a lithium salt, and the lithium salt may be LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiB 10 Cl 10 , LiAlCl 4 , LiAlO 4 , LiPF 6 , LiCF 3 SO 3 , LiCH 3 CO 2 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiCH 3 SO 3 , LiSO 3 F, LiFSI(Lithium bis(fluorosulfonyl)imide, LiN(SO 2 F) 2), LiBETI(lithium bisperfluoroethanesulfonimide, LiN(SO 2 CF 2 CF 3 ) 2 and LiTFSI (lithium(bis)trifluoromethanesulfonimide, LiN(SO 2 CF 3 ) 2 ) may contain one or more selected from the group consisting of

[0069] In one embodiment of the present invention, the concentration of the lithium salt may be 0.1M to 3.0M, preferably 0.5M to 2.5M, and more preferably 0.8M to 2.0M. Specifically, the concentration of the lithium salt may be 0.1M or more, 0.2M or more, 0.3M or more, 0.4M or more, 0.5M or more, 0.6M or more, 0.7M or more, 0.8M or more, 0.9M or more, 1.0M or more, 3.0M or less, 2.5M or less, 2.0M or less, or 1.5M or less. If the concentration of the lithium salt is less than 0.1M, the conductivity of the electrolyte is reduced, resulting in a decrease in electrolyte performance, and if the concentration of the lithium salt is more than 3.0M, the viscosity of the electrolyte is increased, resulting in a decrease in the mobility of lithium ions. Therefore, it is preferable that the concentration of the lithium salt satisfies the above range. The lithium salt acts as a source of lithium ions in the battery, enabling basic operation of the lithium secondary battery.

[0070] In another embodiment of the present invention, the nonaqueous electrolyte for a lithium secondary battery is LiPF 6 and LiPF 6 Other types of lithium salts may be used in combination.

[0071] Said LiPF 6 Other types of lithium salts that are not LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiB 10 Cl 10 , LiAlCl 4 , LiAlO 4 , LiPF6 , LiCF 3 SO 3 , LiCH 3 CO 2 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiCH 3 SO 3 , LiSO 3 F, LiFSI(Lithium bis(fluorosulfonyl)imide, LiN(SO 2 F) 2 ), LiBETI(lithium bisperfluoroethanesulfonimide, LiN(SO 2 CF 2 CF 3 ) 2 and LiTFSI (lithium(bis)trifluoromethanesulfonimide, LiN(SO 2 CF 3 ) 2 ) may be one or more selected from the group consisting of

[0072] In addition, the LiPF 6 and LiPF 6 The molar ratio of the LiPF to other types of lithium salts other than LiPF may be 1:1 to 10:1, preferably 4:1 to 10:1, and more preferably 6:1 to 10:1. 6 and LiPF 6 By satisfying the above molar ratio, other types of lithium salts can stably form a coating film that can suppress the corrosion phenomenon of the current collector while suppressing side reactions of the electrolyte.

[0073] In one embodiment of the present invention, the non-aqueous electrolyte for a lithium secondary battery may include an organic solvent, and the organic solvent may be a solvent commonly used in lithium secondary batteries, such as an ether compound, an ester (acetate, propionate) compound, an amide compound, a linear carbonate, or a cyclic carbonate compound, which may be used alone or in combination.

[0074] Among the listed compounds, it is preferable to use a mixture of linear carbonate and cyclic carbonate as the organic solvent. When a mixture of linear carbonate and cyclic carbonate is used as the organic solvent, the dissociation and movement of lithium salt can be smooth. In this case, the cyclic carbonate compound and the linear carbonate compound may be mixed in a volume ratio of 1:9 to 6:4, preferably in a volume ratio of 1:9 to 4:6, more preferably in a volume ratio of 2:8 to 4:6.

[0075] Meanwhile, specific examples of the linear carbonate compound include one compound selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and ethyl propyl carbonate (EPC), or a mixture of at least two compounds, but are not limited thereto.

[0076] Specific examples of the cyclic carbonate compound include one compound or a mixture of at least two compounds 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 halides thereof.

[0077] In one embodiment of the present invention, a lithium secondary battery including the nonaqueous electrolyte for lithium secondary batteries may have an operating voltage of 4.0 V or more, preferably 4.1 V or more, and more preferably 4.2 V or more. When the operating voltage of the lithium secondary battery is less than 4.0 V, the addition of the phosphoric acid-based additive of the present invention does not make much difference, but in lithium secondary batteries having an operating voltage of 4.0 V or more, the addition of the additive shows an effect of rapidly increasing high-temperature storage safety and capacity characteristics.

[0078] Lithium secondary battery The lithium secondary battery according to the present invention will now be described.

[0079] The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte for lithium secondary batteries. More specifically, the lithium secondary battery includes at least one positive electrode, at least one negative electrode, a separator that may be selectively interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte for lithium secondary batteries. Here, the non-aqueous electrolyte for lithium secondary batteries is the same as that described above, and therefore a detailed description thereof will be omitted.

[0080] (1) Positive electrode The positive electrode may be prepared by coating a positive electrode current collector with a positive electrode active material slurry including a positive electrode active material, an electrode binder, an electrode conductive material, a solvent, etc. The positive electrode may have a layered structure based on the positive electrode active material.

[0081] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In this case, the positive electrode current collector may have fine irregularities on its surface to strengthen the binding force of the positive electrode active material, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0082] The positive electrode active material can be a compound capable of reversible intercalation and deintercalation of lithium, and specifically, can include a lithium composite metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium composite metal oxide is a lithium-manganese-based oxide (for example, LiMnO 2 、LiMn 2 O 4 etc.), a lithium-cobalt-based oxide (for example, LiCoO 2 etc.), a lithium-nickel-based oxide (for example, LiNiO 2 etc.), a lithium-nickel-manganese-based oxide (for example, LiNi 1‐Y1 Mn Y1 O 2 (where 0 < Y1 < 1), LiMn 2‐z1 Ni z1 O 4 (where 0 < Z1 < 2) etc.), a lithium-nickel-cobalt-based oxide (for example, LiNi 1‐Y2 Co Y2 O 2 (where 0 < Y2 < 1) etc.), a lithium-manganese-cobalt-based oxide (for example, LiCo 1‐Y3 Mn Y3 O 2 (where 0 < Y3 < 1), LiMn 2‐z2 Co z2 O 4 (where 0 < Z2 < 2) etc.), a lithium-nickel-manganese-cobalt-based oxide (for example, Li(Ni p1 Co q1 Mn r1 )O 2 (where 0 < p1 < 1, 0 < q1 < 1, 0 < r1 < 1, p1 + q1 + r1 = 1) or Li(Ni p2 Co q2 Mn r2 )O 4 (where 0 < p2 < 2, 0 < q2 < 2, 0 < r2 < 2, p2 + q2 + r2 = 2) etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Ni p3 Co q3 Mnr3 M S1 )O 2 (Here, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p3, q3, r3, and s1 are the atomic fractions of independent elements, respectively, where 0 < p3 < 1, 0 < q3 < 1, 0 < r3 < 1, 0 < s1 < 1, and p3 + q3 + r3 + s1 = 1), etc.) etc. can be mentioned, and any one or two or more of these compounds can be included.

[0083] Among these, the lithium composite metal oxide can enhance the capacity characteristics and stability of the battery. Thus, 2 LiCoO 2 、LiMnO 2 、LiNiO 0.6 、lithium nickel manganese cobalt oxide (e.g., Li(Ni 0.2 Mn 0.2 )O 2 、Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 、or Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 etc.), or lithium nickel cobalt aluminum oxide (e.g., LiNi 0.8 Co 0.15 Al 0.05 O 2 etc.) etc. may be used. When considering the remarkable improvement effect by controlling the type and content ratio of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O 2 、Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 、Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 、Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 or Li(Ni0.85 Mn 0.08 Co 0.05 Al 0.02 )O 2 etc., and any one of these may be used alone or in combination of two or more.

[0084] In addition, the positive electrode active material may include a lithium transition metal composite oxide in which the nickel content of the total transition metals is 60 atm% or more, for example, 60 atm% or more, 65 atm% or more, 70 atm% or more, 75 atm% or more, 80 atm% or more, 85 atm% or more, or 90 atm% or more.

[0085] The electrode binder is a component that aids in binding the positive electrode active material and the electrode conductive material, etc., and in binding to the current collector. Specific examples of the electrode binder include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0086] The electrode conductive material is a component for further improving the conductivity of the positive electrode active material. The electrode conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and may be, for example, graphite; carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, and other carbon-based materials; 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. Specific examples of commercially available conductive materials include acetylene black-based materials (products of Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC-based materials (products of Armak Company), Vulcan XC-72 (products of Cabot Company), and Super P (products of Timcal Corporation).

[0087] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desired viscosity when the positive electrode active material, and optionally a positive electrode binder and a positive electrode conductive material, are included.

[0088] (2) Negative electrode The negative electrode may be prepared by coating a negative electrode current collector with a negative electrode active material slurry including a negative electrode active material, an electrode binder, an electrode conductive material, a solvent, etc. Meanwhile, the negative electrode may be prepared by using a metal negative electrode current collector itself as an electrode.

[0089] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, aluminum-cadmium alloy, etc. Also, like 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, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0090] The negative electrode active material may be at least one selected from the group consisting of natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxide (LTO), metals (Me) which are Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe; alloys composed of the metals (Me); oxides (MeOx) of the metals (Me); and composites of the metals (Me) and carbon.

[0091] The electrode binder, the electrode conductive material, and the solvent are the same as those described above, and therefore detailed description thereof will be omitted.

[0092] (3) Separation membrane The separator may be a conventional porous polymer film used in a conventional separator, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, which may be used alone or in combination. Alternatively, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high melting point glass fiber, a polyethylene terephthalate fiber, or the like, may be used, but is not limited thereto.

[0093] In the following, preferred examples are presented to aid in understanding the present invention. However, the following examples are provided merely to facilitate understanding of the present invention, and the present invention is not limited thereto.

[0094] Working Example Example 1 Li(Ni 0.85 Mn 0.08 Co 0.05 Al 0.02 )O 2 Carbon black as a conductive material and PVDF as a binder were prepared in a weight ratio of 97.6:1.2:1.2 (positive electrode active material: conductive material: binder), and mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The prepared positive electrode active material slurry was applied to one side of an aluminum current collector (15 μm) (loading amount: 0.40 to 0.55 mg / 25 cm). 2 ), dried at 130° C. for 20 minutes or more, and then rolled once or twice to a porosity of 24% to prepare a positive electrode.

[0095] The negative electrode was made of a mixture of natural graphite and artificial graphite in a ratio of 2:8, and a porous polyethylene separator was placed between the positive and negative electrodes to prepare an electrode assembly. The electrode assembly was placed inside a battery case, and an electrolyte was injected into the case to prepare a lithium secondary battery. The electrolyte was a 1M solution of lithium hexafluorophosphate (LiPF 6 ) was dissolved, 0.5 wt% vinylene carbonate (VC), 0.5 wt% propane sultone (PS) and 1 wt% ethylene sulfate (ESa) were added, and 0.5 wt% of a phosphoric acid additive in which all R in Chemical Formula 1 are allyl groups was added to prepare the polymer.

[0096] Example 2 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 1 wt % of a phosphoric acid-based additive was added to the electrolyte.

[0097] Example 3 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 3 wt % of a phosphoric acid-based additive was added to the electrolyte.

[0098] Example 4 A lithium secondary battery was manufactured in the same manner as in Example 2, except that a phosphate-based additive in which all R's are F in Chemical Formula 1 was used in the electrolyte.

[0099] Example 5 In the electrolyte, all R in formula 1 are CF 3 A lithium secondary battery was manufactured in the same manner as in Example 2, except that a phosphoric acid-based additive was used.

[0100] Example 6 A lithium secondary battery was manufactured in the same manner as in Example 1, except that 5 wt % of a phosphoric acid-based additive was added to the electrolyte.

[0101] Comparative Example 1 A lithium secondary battery was manufactured in the same manner as in Example 1, except that no phosphoric acid-based additive was added to the electrolyte.

[0102] Experimental Example Experimental example: High temperature performance measurement The lithium secondary batteries prepared in Examples 1 to 6 and Comparative Example 1 were charged to 100% SOC (2000 mAh) under a voltage condition of 4.2 V. Thereafter, after storing at high temperature for 8 weeks in a thermostatic chamber at 60° C., the capacity retention rate (%), resistance increase rate (%), and volume increase rate (%) were measured and are shown in Table 1 below.

[0103] [Table 1]

[0104] * Capacity retention rate (%): Using PNEsolution PEBC0506, charge with CC / CV (0.33C CC / 4.2V 0.05C Current-cut CV) and leave for 30 minutes, then discharge with CC (0.33) three times, and the third discharge capacity was reflected as the capacity. Capacity maintenance rate (%)=(Nth week capacity) / (Initial capacity)×100

[0105] * Resistance increase rate (%): Using PNEsolution's PEBC0506, the discharge capacity standard was set to SOC 50, and the resistance was measured during CC pulse discharge at a current of 2.5C. Resistance = (voltage difference before and after discharge pulse) / (current during discharge) Resistance increase rate (%) = (Nth week resistance - initial resistance) / (initial resistance) x 100

[0106] * Volume increase rate (%): Using TWD-PLS's TWD-150DM, set the sample to SOC 100 before high-temperature storage, and then measure the initial volume. Immediately after high-temperature storage, cool the sample to room temperature and then measure the volume. Volume increase rate (%) = (volume at Nth week - initial volume) / (initial volume) x 100

[0107] 1) This refers to the phenomenon in which the internal pressure of the battery increases due to the generation of gas above a certain volume, and the internal pressure is exposed to the outside air while pressing the sealing part.

[0108] From Table 1, it can be seen that the lithium secondary batteries (Examples 1 to 6) having the phosphoric acid-based additive added to the electrolyte according to the present invention not only have a high capacity retention rate after high-temperature storage, but also have a low resistance increase rate and volume increase rate, and thus have significantly improved high-temperature stability compared to the lithium secondary battery (Comparative Example 1) not having the phosphoric acid-based additive added to the electrolyte.

[0109] Any simple modifications or variations of the present invention belong to the scope of the present invention, and the specific scope of protection of the present invention will be defined by the appended claims.

Claims

1. A non-aqueous electrolyte for a lithium secondary battery, comprising a lithium salt, an organic solvent, and a phosphoric acid additive represented by the following Chemical Formula 1: 【Chemistry 1】 In the above Chemical Formula 1, The R is a chain or ring-type functional group containing at least one element selected from the group consisting of H, C, N, O, F, P, S, and Si.

2. The R's are the same or different and each independently represent hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted mercapto, substituted or unsubstituted carbamoyl, substituted or unsubstituted C １‐７ Alkyl, substituted or unsubstituted C １‐７ Alkyl halides, substituted or unsubstituted C ２‐７ Alkenyl, substituted or unsubstituted C ２‐７ Alkynyl, substituted or unsubstituted C １‐７ Alkoxy, substituted or unsubstituted C １‐４ Alkoxy-C １‐４ Alkoxy, substituted or unsubstituted C ６‐１０ Aryl-C １‐４ Alkoxy, substituted or unsubstituted C ２‐７ Alkenyloxy, substituted or unsubstituted C ２‐７ Alkynyloxy, substituted or unsubstituted C ３‐７ Cycloalkyl, substituted or unsubstituted C ３‐７ Cycloalkenyl, substituted or unsubstituted 3-7 membered heterocycloalkyl, substituted or unsubstituted C ３‐７ Cycloalkyloxy, substituted or unsubstituted C ３‐７ Cycloalkenyloxy, substituted or unsubstituted 3-7 membered heterocycloalkyloxy, substituted or unsubstituted C ６‐１０ Aryl, substituted or unsubstituted 5-10 membered heteroaryl, substituted or unsubstituted C ６‐１０ Aryloxy, substituted or unsubstituted 5-10 membered heteroaryloxy, substituted or unsubstituted mono- or di-C １‐４ Alkylamino, substituted or unsubstituted mono- or di-C ６‐１０ Arylamino, substituted or unsubstituted C １‐４ Alkylcarbonylamino, substituted or unsubstituted C １‐４ Alkylcarbonyl, substituted or unsubstituted C １‐４ Alkoxycarbonyl, substituted or unsubstituted C ２‐４ Alkenyloxycarbonyl, and substituted or unsubstituted C ２‐４ 2. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the non-aqueous electrolyte is selected from the group consisting of alkynyloxycarbonyl.

3. The R's are the same or different, and each R is independently selected from hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted C １‐４ Alkyl, substituted or unsubstituted C １‐４ Alkyl halides, substituted or unsubstituted C ２‐４ Alkenyl, substituted or unsubstituted C ２‐４ Alkynyl, substituted or unsubstituted C １‐４ Alkoxy, substituted or unsubstituted mono- or di-C １‐４ Alkylamino, substituted or unsubstituted C １‐４ Alkylcarbonyl, and substituted or unsubstituted C １‐４ 3. The non-aqueous electrolyte for a lithium secondary battery according to claim 2, wherein the non-aqueous electrolyte is selected from the group consisting of alkoxycarbonyls.

4. The R's are the same or different, and each R is independently selected from hydrogen, halogen, substituted or unsubstituted C １‐４ Alkyl, substituted or unsubstituted C １‐４ Alkyl halides and substituted or unsubstituted C ２‐４ The non-aqueous electrolyte for a lithium secondary battery according to claim 3, wherein the alkyl group is selected from the group consisting of alkenyl.

5. 2. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the phosphoric acid-based additive is contained in an amount of 0.01 to 10% by weight based on the total weight of the electrolyte.

6. The lithium salt is LiCl, LiBr, LiI, LiBF ４ , LiClO ４ , LiB １０ C １０ , LiAlCl ４ , LiAlO ４ , LiPF ６ , LiCF ３ SO ３ , LiCH ３ CO ２ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiCH ３ SO ３ , LiSO ３ F, LiN (SO ２ F) ２ , LiN(SO ２ CF ２ CF ３ ) ２ and LiN(SO ２ CF ３ ) ２ The non-aqueous electrolyte for a lithium secondary battery according to claim 1, selected from the group consisting of:

7. 2. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the concentration of the lithium salt is 0.1M to 3M.

8. 2. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the organic solvent comprises at least one selected from the group consisting of ethers, esters, amides, linear carbonates, and cyclic carbonates.

9. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the nonaqueous electrolyte for a lithium secondary battery according to any one of claims 1 to 8.

10. 10. The lithium secondary battery according to claim 9, wherein the positive electrode has a layered structure based on a positive electrode active material, and the positive electrode active material includes a lithium composite transition metal oxide in which the nickel content of all transition metals is 60 atm % or more.

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