KR20230069830A - Nonaqueous electrolyte for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

A non-aqueous electrolyte for a lithium secondary battery including lithium salt, an organic solvent, and a phosphoric acid-based additive represented by chemical formula 1 is provided. By adding the phosphoric acid-based additive according to one embodiment of the present invention to the electrolyte, the high-temperature stability of a lithium secondary battery can be significantly improved. In chemical formula 1, R is a functional group with a chain or ring structure including one or more elements selected from a group consisting of H, C, N, O, F, P, S, and Si.

Description

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

The present invention relates to a non-aqueous electrolyte solution for a secondary battery capable of improving high-temperature storage characteristics and lifespan characteristics of a lithium secondary battery and a lithium secondary battery including the same.

Recently, as the application areas of lithium secondary batteries are rapidly expanding not only to the power supply of electronic devices such as electricity, electronics, communication, and computers, but also to the power storage and supply of large-area devices such as automobiles and power storage devices, The demand for a stable secondary battery is increasing.

A lithium secondary battery is generally composed of a “cathode” active material made of lithium-containing transition metal oxide, or a mixture of a carbon material or silicon material “cathode” active material capable of occluding and releasing lithium ions, and optionally a binder and a conductive material, respectively, as a “cathode” current collector. And "negative electrode" is applied to the current collector to manufacture "positive electrode" and "negative electrode", and then laminated on both sides of the separator to form an electrode current collector of a predetermined shape, and then the electrode current collector and the non-aqueous electrolyte are inserted into the "battery" case. Here, in order to secure the performance of the battery, it almost inevitably undergoes formation (formation) and aging (aging) processes.

The formation process is a step of activating a secondary battery by repeating charging and discharging after assembling the battery, and during the charging, lithium ions from a lithium-containing transition metal oxide used as a positive electrode move to and insert into a carbonaceous negative electrode active material used as a negative electrode. do. At this time, highly reactive lithium ions react with the electrolyte to generate compounds such as Li ₂ CO ₃ , Li ₂ O, LiOH, and LiF, and these compounds form a solid electrolyte interface (SEI) layer on the electrode surface. . The formation of the SEI layer is an important factor because the SEI layer closely affects lifespan and capacity retention.

In recent years, especially in lithium secondary batteries for automobiles, high capacity, high output, and long lifespan characteristics have become important. In order to achieve high capacity, the positive electrode active material with high energy density but low stability is used on the side of the positive electrode, so it is necessary to form an active material-electrolyte interface that can stabilize the positive electrode active material by protecting the surface of the positive electrode active material. In 　, the surface paper of the cathode is decomposed into the electrolyte and causes side reactions.

Specifically, lithium ion batteries often use high-voltage and high-content nickel cathodes in order to secure current energy density. As the voltage of the battery increases, electrochemical side reactions on the surface of the cathode increase, and nickel-cobalt-manganese ( In the case of the NCM) cathode, as the nickel content increases, structural instability increases, which may promote decomposition of the electrolyte. At this time, the solvent is decomposed to generate gas or resistance is increased, and HF is generated by salt decomposition to accelerate the elution of the transition metal from the cathode active material, which is a metal oxide. In addition, by destroying the SEI layer formed on the surface of _the active material, problems such as increased resistance and deterioration of battery life may occur. Side reactions at additional electrodes may occur.

Therefore, in order to solve the above problems, research on forming a solid SEI layer capable of suppressing side reactions during high-temperature storage is continuing in the related art, and as part of this, research on additives in the electrolyte is also continuing.

Republic of Korea Patent Publication No. 10-2011-0116019 Republic of Korea Patent Publication No. 10-2015-0089712

The present invention is to solve the conventional problems, and as an additive to a non-aqueous electrolyte solution for a lithium secondary battery, it is possible to form a film capable of effectively suppressing side reactions on the surface of a positive electrode and a negative electrode that inevitably occur in a lithium secondary battery. It is intended to provide an electrolyte solution for a lithium secondary battery capable of improving high-temperature storage characteristics and lifespan characteristics of a lithium secondary battery including a phosphoric acid-based additive having an excellent specific structure.

In addition, the present invention is intended to provide a lithium secondary battery having significantly improved battery durability, that is, high-temperature storage characteristics and lifespan characteristics, by including the non-aqueous electrolyte solution for a lithium secondary battery, so that a film can be formed on the surface of the positive electrode and the negative electrode. .

In order to achieve the above object, the present invention provides a non-aqueous electrolyte solution for a lithium secondary battery including a lithium salt, an organic solvent, and a phosphoric acid-based additive represented by Formula 1 below.

[Formula 1]

In Formula 1,

R is a functional group that helps film formation, and is a functional group having a chain or cyclic structure containing at least one element selected from H, C, N, O, F, P, S, and Si.

In addition, in one embodiment of the present invention, R in Formula 1 is the same as or different from each other, and each independently represents 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 halogenated alkyl, substituted or unsubstituted C _2-7 alkenyl, substituted or unsubstituted C 1-7 substituted 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 1-4} alkoxycarbonyl It provides a non-aqueous electrolyte solution for a lithium secondary battery, which is selected from the group consisting of cyclic C _2-4 alkynyloxycarbonyl.

In an embodiment of the present invention, R in Formula 1 is the same as or different from each other, and each independently represents hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted C _{1 -4} alkyl, substituted or unsubstituted C _1-4 halogenated alkyl, substituted or unsubstituted C _2-4 alkenyl, and substituted or unsubstituted C _2-4 alkynyl, substituted or unsubstituted C _1-4 selected from the group consisting of 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 alkoxycarbonyl It provides a non-aqueous electrolyte solution for a lithium secondary battery.

In one embodiment of the present invention, R in Formula 1 is the same as or different from each other, and each independently hydrogen, halogen, substituted or unsubstituted C _1-4 alkyl, substituted or unsubstituted C _1-4 halogenated alkyl , And a substituted or unsubstituted C _2-4 It provides a non-aqueous electrolyte solution for a secondary battery selected from the group consisting of alkenyl.

One embodiment of the present invention provides a non-aqueous electrolyte solution for a lithium secondary battery, in which the phosphoric acid-based additive is included in an amount of 0.01% to 10% by weight based on the total weight of the electrolyte solution.

In one embodiment of the present invention, the lithium salt is 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 ), which is selected from the group consisting of, to provide a non-aqueous electrolyte solution for a lithium secondary battery.

One embodiment of the present invention provides a non-aqueous electrolyte solution for a lithium secondary battery in which the concentration of the lithium salt is 0.1M to 3M.

One embodiment of the present invention provides a non-aqueous electrolyte solution 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.

One 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 the non-aqueous electrolyte for the lithium secondary battery.

One embodiment of the present invention provides a lithium secondary battery in which the positive electrode includes a lithium composite transition metal oxide having a layered structure as a positive electrode active material and having a nickel content of 60 atm% or more among the total transition metals.

The non-aqueous electrolyte for a lithium secondary battery according to the present invention includes a phosphoric acid-based additive having a specific structure, thereby suppressing the decomposition reaction of the non-aqueous electrolyte itself and forming a film on the surface of the positive and negative electrodes, which inevitably occurs in the lithium secondary battery. It shows the effect of effectively suppressing side reactions on the surface of the anode and cathode.

Due to this, an effect of improving durability, that is, high-temperature storage characteristics and lifespan characteristics of a lithium secondary battery including the non-aqueous electrolyte solution for a lithium secondary battery is exhibited.

The embodiments provided according to the present invention can all be achieved by the following description. The following description should be understood to describe preferred embodiments of the present invention, and it should be understood that the present invention is not necessarily limited thereto.

As used herein, the term “C _n1-n2 ” means that the number of carbon atoms in the functional group is n1 to n2.

As used herein, the term “alkyl” refers to a straight-chain or branched-chain saturated hydrocarbon containing one radical, and one radical determines the binding site as a functional group, and the binding site is not particularly limited. Examples of the term “alkyl” include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl, and hexyl. don't

As used herein, the term "alkylene" refers to a straight-chain or branched-chain saturated hydrocarbon containing two radicals, each of the two radicals determining a binding site as a functional group, and the binding site is not particularly limited. Examples of the term “alkylene” include, but are not limited to, methylene and ethylene.

As used herein, the term "alkenyl" includes one radical and refers to a straight or branched chain hydrocarbon having at least one carbon-carbon double bond, one radical as a functional group determining the bonding site, and the bonding site is not particularly limited. Examples of the term "alkenyl" include, but are not necessarily limited to, ethenyl and propenyl, and the like.

As used herein, the term "alkynyl" includes one radical and means a straight or branched chain hydrocarbon having at least one carbon-carbon triple bond, one radical as a functional group determining the bonding site, and the bonding site is not particularly limited. Examples of the term "alkynyl" include, but are not necessarily limited to, acetylenyl and 1-propynyl.

As used herein, the term “halogen” means fluorine (F), chlorine (Cl), bromine (Br) or iodine (I).

As used herein, the term "halogenated alkyl" means that one or more hydrogens in an alkyl are replaced with a halogen.

As used herein, the term "cycloalkyl" includes one radical and means a saturated hydrocarbon having one or more rings, and one radical determines the binding site as a functional group, and the binding site is not particularly limited. Examples of the term “cycloalkyl” include, but are not necessarily limited to, cyclopentyl, cyclohexyl, and cycloheptyl.

As used herein, the term “cycloalkenyl” refers to a hydrocarbon containing one radical, having one or more rings, and having one or more carbon-carbon double bonds in the ring, wherein one radical is a functional group, indicating a bonding position. determined, and the binding site is not particularly limited. Examples of the term “cycloalkenyl” include, but are not necessarily limited to, cyclopentenyl, cyclohexenyl, and cycloheptenyl.

As used herein, the term “n ₁ -n ₂ member” means that the sum of the number of carbon atoms and the number of hetero atoms is n ₁ to n ₂ . A hetero element broadly means an element other than carbon, but in this specification, the term “n ₁ -n ₂ member” is used in front of a cyclic functional group to indicate the number of elements constituting the ring.

As used herein, the term "heterocycloalkyl" refers to a saturated hydrocarbon containing one radical, having one or more rings, and having one or more heteroatoms in the ring, wherein one radical determines the bonding site as a functional group and , the bonding position is not particularly limited. The hetero element may form a ring, and exemplarily includes O, N, S, P, and the like. Examples of the term “heterocycloalkyl” include, but are not necessarily limited to, piperidinyl and tetrahydropyranyl.

As used herein, the term "aryl" includes one radical and refers to an aromatic cyclic hydrocarbon having one or more rings, and one radical determines the binding site as a functional group, and the binding site is not particularly limited. Examples of the term “aryl” include, but are not necessarily limited to, phenyl and naphthyl, and the like.

As used herein, the term "arylene" includes two radicals and refers to an aromatic cyclic hydrocarbon having at least one ring, each of the two radicals determining a bonding site as a functional group, and the bonding position is not particularly limited. don't Examples of the term “arylene” include, but are not limited to, phenylene and naphthylene. The aforementioned “alkylene” and “arylene” may be combined and used in the form of, for example, methylene-phenylene.

As used herein, the term "heteroaryl" refers to an aromatic cyclic hydrocarbon containing one radical, having one or more rings, and one or more heteroatoms in the ring, one radical being a functional group, determining the bonding site. And, the bonding position is not particularly limited. The hetero element may form a ring, and exemplarily includes O, N, S, and the like. Examples of the term “heteroaryl” include, but are not necessarily limited to, pyrrolyl and furanyl.

As used herein, the term "alkoxy" refers to a functional group of the form -OR _a where R _a is an alkyl as described above. Examples of the term “alkoxy” include, but are not necessarily limited to, methoxy, difluoromethoxy, trifluoromethoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy and t-butoxy, and the like It doesn't work.

As used herein, the term "alkoxy-alkoxy" refers to a functional group of the form -OR _a -OR _b where R _a is alkylene and R _b is the aforementioned alkyl. Examples of the term “alkoxy-alkoxy” include, but are not necessarily limited to, methoxy-methoxy, methoxy-ethoxy, and ethoxy-ethoxy.

As used herein, the term “aryl-alkoxy” refers to a functional group of the form -OR _a -R _b where R _a is alkylene and R _b is the aforementioned aryl. Examples of the term “aryl-alkoxy” include, but are not necessarily limited to, phenyl-methoxy and phenyl-ethoxy.

As used herein, the term “alkenyloxy” refers to a functional group of the form —OR _a where R _a is alkenyl as described above. Examples of the term “alkenyloxy” include, but are not necessarily limited to, ethenyloxy and propenyloxy.

As used herein, the term “alkynyloxy” refers to a functional group of the form —OR _a where R _a is alkynyl as described above. Examples of the term “alkynyloxy” include, but are not necessarily limited to, ethynyloxy and propynyloxy.

As used herein, the term “cycloalkyloxy” refers to a functional group of the form —OR _a where R _a is a cycloalkyl as described above. Examples of the term “cycloalkyloxy” include, but are not necessarily limited to, cyclopentyloxy and cyclohexyloxy.

As used herein, the term "cycloalkenyloxy" refers to a functional group of the form -OR _a where R _a is the aforementioned cycloalkenyl. Examples of the term “cycloalkenyloxy” include, but are not necessarily limited to, cyclopentenyloxy and cyclohexenyloxy.

As used herein, the term “heterocycloalkyloxy” refers to a functional group of the form —OR _a where R _a is the aforementioned heterocycloalkyl. Examples of the term “heterocycloalkyloxy” include, but are not necessarily limited to, piperidinyloxy and tetrahydropyranyloxy.

As used herein, the term “aryloxy” refers to a functional group of the form —OR _a where R _a is the aforementioned aryl. Examples of the term “aryloxy” include, but are not necessarily limited to, phenyloxy and naphthyloxy.

As used herein, the term “heteroaryloxy” refers to a functional group of the form —OR _a where R _a is the aforementioned heteroaryl. Examples of the term “heteroaryloxy” include, but are not necessarily limited to, pyrrolyloxy and furanyloxy.

As used herein, the term "mercapto" refers to a functional group of the form -SH.

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

As used herein, the term "amino" refers to a functional group of the form -NH ₂ . The amino may be substituted with one or more hydrogens such as the aforementioned alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl. For example, when one hydrogen in the amino is substituted with an alkyl, it is termed a mono-alkylamino, and when two hydrogens in the amino are substituted with an alkyl, it is termed a di-alkylamino.

As used herein, the term "carbonylamino" refers to a functional group of the form -NHC(O ₎ R a where R _a is an alkyl, cycloalkyl, heterocycloalkyl, aryl or heteroaryl, etc. as described above. Here, hydrogen may also be substituted with an alkyl or the like.

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

As used herein, the term “carbamoyl” refers to a functional group in the form of —C(O)NH ₂ . Here, one or more hydrogens may also be substituted with alkyl or the like.

As used herein, the term “nitro” refers to a functional group in the form of —NO ₂ .

As used herein, the term "carbonyl" refers to a compound of the form -C(O ₎ R _a where R a is an alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, alkoxy, alkenyloxy, alkynyloxy, etc., as described above. means a functional group. For example, when R _a is alkyl, it is also termed “alkylcarbonyl”, and when R _a is alkoxy, it is also termed “alkoxycarbonyl”. In addition, when R _a is alkenyloxy, it is also named “alkenyloxycarbonyl”, and when R _a is alkynyloxy, it is also named “alkynyloxycarbonyl”.

As used herein, the term “substituted or unsubstituted” means that the corresponding functional group exists in a substituted or unsubstituted state, and substitution means that a hydrogen atom bonded to a carbon atom of a compound is changed to another substituent, and the substituted The position is not limited as long as it is a position where a hydrogen atom is substituted, that is, a position where a substituent can be substituted, and when two or more substituents are substituted, two or more substituents may be the same or different from each other.

As long as the substituent is a substituent commonly used in the art, it may be used without particular limitation. The substituents are, for example, halogen, hydroxy, cyano, nitro, amino, C _1-4 alkyl, C _1-4 halogenated alkyl, 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, C _1-4 alkylcarbonyl, C _1-4 alkoxycarbonyl, C _2-4 alkenyloxycarbonyl, and C _2-4 alkynyloxycarbonyl and the like.

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

The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery including a lithium salt, an organic solvent, and a phosphoric acid-based additive represented by Formula 1 below.

[Formula 1]

In Formula 1,

R is a functional group that helps film formation, and is a functional group having a chain or cyclic structure containing at least one element selected from H, C, N, O, F, P, S, and Si.

In one embodiment of the present invention, R in Formula 1 is the same as or different from each other, and each independently represents hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted mer, Capto, substituted or unsubstituted carbamoyl, substituted or unsubstituted C _1-7 alkyl, substituted or unsubstituted C _1-7 halogenated alkyl, 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 cyclo Alkenyl, 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 Member 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 alkylcarbo Nylamino, 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 1-4 alkoxycarbonyl It may be selected from the group consisting of C _2-4 alkynyloxycarbonyl.

In another embodiment of the present invention, R in Formula 1 is the same as or different from each other, and each independently represents hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted C _1-4 alkyl, substituted or unsubstituted C _1-4 halogenated alkyl, substituted or unsubstituted C _2-4 alkenyl, and substituted or unsubstituted C _2-4 alkynyl, substituted or unsubstituted C _{1- 4} from the group consisting of 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 alkoxycarbonyl may be selected.

In another embodiment of the present invention, in Formula 1, R is the same as or different from each other, and each independently hydrogen, halogen, substituted or unsubstituted C _1-4 Alkyl, substituted or unsubstituted C _1-4 It may be selected from the group consisting of halogenated alkyl and substituted or unsubstituted C _2-4 alkenyl.

In one embodiment of the present invention, the phosphoric acid-based additive may be included in an amount of 0.01% to 10% by weight based on the total weight of the electrolyte solution. Specifically, the phosphoric acid-based additive is 0.01% by weight or more, 0.05% by weight or more, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, 10% by weight or less, 9% by weight or more, based on the total weight of the electrolyte. 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, 0.01 wt% to 10 wt%, 0.1 wt% to 5 wt% , 0.5% by weight to 3% by weight, it may be 1% by weight to 3% by weight. When the content of the phosphoric acid-based additive is less than the above range, there is no effect of addition, such as suppressing swelling of the battery or insignificant improvement in the capacity retention rate during high-temperature storage or long-term battery operation, and the resistance increase rate of the lithium secondary battery When the content of the phosphoric acid-based additive exceeds the above range, the resistance increases excessively, resulting in a rapid deterioration in life, and the characteristics of the lithium secondary battery are rather deteriorated. do. Therefore, it is preferable that the content of the phosphoric acid-based additive satisfies the above range.

In one embodiment of the present invention, the non-aqueous electrolyte solution for a lithium secondary battery, lithium difluoro oxalate borate (LiDFOB), lithium bisoxalate borate (LiB (C ₂ O ₄ ) ₂ , LiBOB), lithium tetrafluoro Roborate (LiBF ₄ ), lithium difluorooxalatophosphate (LiDFOP), lithium tetrafluoro oxalatophosphate (LiTFOP), lithium difluorophosphate (LiPO ₂ F ₂ ), fluoroethylene carbonate (FEC), vinyl Ren carbonate (VC), vinyl ethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, ethylene sulfate, propylene sulfite, diallyl sulfonate sulfonate), ethane sultone, propane sulton (PS), butane sultone (butane sulton), ethene sultone, butene sultone and propene sultone (propene sultone (PRS)) may further include an additive selected from the group consisting of.

In one embodiment of the present invention, the non-aqueous electrolyte for a lithium secondary battery may include a lithium salt, and the lithium salt is 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 ) It may include one or more selected from the group consisting of.

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, more preferably 0.8M to 2.0M. Specifically, the concentration of the lithium salt is 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 It may be less than or equal to 2.5M, less than or equal to 2.0M, or less than or equal to 1.5M. If the concentration of the lithium salt is less than 0.1 M, the conductivity of the electrolyte solution is lowered and the performance of the electrolyte solution is deteriorated. If the concentration exceeds 3.0 M, the viscosity of the electrolyte solution increases and the mobility of lithium ions decreases. Therefore, the concentration of the lithium salt preferably satisfies the above range. The lithium salt serves as a source of lithium ions in the battery, enabling basic operation of the lithium secondary battery.

In another embodiment of the present invention, the non-aqueous electrolyte for a lithium secondary battery may be used by mixing LiPF ₆ and other types of lithium salts other than LiPF ₆ .

Lithium salts other than LiPF ₆ include 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 ) It may be one or more selected from the group consisting of.

In addition, the molar ratio between LiPF ₆ and a lithium salt other than LiPF ₆ may be 1:1 to 10:1, preferably 4:1 to 10:1, and more preferably 6:1 to 10:1. It may be 10:1. By satisfying the molar ratio between LiPF ₆ and a type of lithium salt other than LiPF ₆ , it is possible to stably form a film capable of suppressing corrosion of a current collector while suppressing a side reaction of the electrolyte solution.

In one embodiment of the present invention, the non-aqueous electrolyte solution for a lithium secondary battery may include an organic solvent, and the organic solvent is a solvent commonly used in a lithium secondary battery, for example, an ether compound, an ester (Acetate , Propionates) compounds, amide compounds, linear carbonate or cyclic carbonate compounds, etc. may be used alone or in combination of two or more.

Among the compounds listed above, preferably, as an organic solvent, a mixture of linear carbonate and cyclic carbonate can be used. As the organic solvent, when linear carbonate and cyclic carbonate are mixed and used, dissociation and movement of the lithium salt can be smoothly performed. At this time, the cyclic carbonate-based compound and the linear carbonate-based compound may be mixed in a volume ratio of 1:9 to 6:4, preferably 1:9 to 4:6, and more preferably 2:8 to 4:6 can

Meanwhile, specific examples of the linear carbonate compound include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC) and ethylpropyl carbonate (EPC). One compound or a mixture of at least two or more selected from the group consisting of, and the like, but is not limited thereto.

In addition, specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3- and a single compound selected from the group consisting of pentylene carbonate, vinylene carbonate, and halides thereof, or a mixture of at least two or more thereof.

In one embodiment of the present invention, the lithium secondary battery including the non-aqueous electrolyte solution for lithium secondary batteries may have an operating voltage of 4.0V or more, preferably 4.1V or more, more preferably It may have an operating voltage of 4.2V or higher. When the operating voltage of the lithium secondary battery is less than 4.0V, the difference according to the addition of the phosphoric acid-based additive of the present invention is not large, but in the lithium secondary battery having an operating voltage of 4.0V or more, high temperature storage safety and capacity according to the addition of the additive It shows the effect of rapidly increasing the characteristics.

lithium secondary battery

Hereinafter, a lithium secondary battery according to the present invention will be described.

The lithium secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution for a lithium secondary battery. More specifically, it includes at least one positive electrode, at least one negative electrode, a separator that can be selectively interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte for a lithium secondary battery. In this case, since the content of the non-aqueous electrolyte for a lithium secondary battery is the same as that described above, a detailed description thereof will be omitted.

(1) anode

The cathode may be prepared by coating a cathode active material slurry including a cathode active material, an electrode binder, an electrode conductive material, and a solvent on a cathode current collector. In addition, the positive electrode may have a layered structure as a positive electrode active material.

The cathode current collector is not particularly limited as long as it does not cause chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon on the surface of aluminum or stainless steel. , those surface-treated with nickel, titanium, silver, etc. may be used. At this time, the positive electrode current collector may form fine irregularities on the surface to enhance the bonding strength of the positive electrode active material, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric.

The cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide containing lithium and at least one metal such as cobalt, manganese, nickel, or aluminum. there is. More specifically, the lithium composite metal oxide is lithium-manganese-based oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt-based oxide (eg, LiCoO _{2 ,} etc.), lithium-nickel-based oxide (eg, LiNiO _{2 ,} etc.), lithium-nickel-manganese oxide (eg, LiNi _1-Y1 Mn _Y1 O ₂ (where 0<Y1<1), LiMn _2-z1 Ni _z1 O ₄ ( Here, 0<Z1<2), etc.), lithium-nickel-cobalt-based oxide (eg, LiNi _1-Y2 Co _Y2 O ₂ (here, 0<Y2<1), etc.), lithium-manganese-cobalt based oxides (e.g., LiCo _1-Y3 Mn _Y3 O ₂ (where 0<Y3<1), LiMn _2-z2 Co _z2 O ₄ (where 0<Z2<2), etc.), 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 lithium- Nickel-Cobalt-transition metal (M) oxides (eg, Li(Ni _p3 Co _q3 Mn _r3 M _S1 ) O ₂ where M is Al, Fe, V, Cr, Ti, Ta, Mg and Mo selected from the group consisting of, p3, q3, r3 and s1 are atomic fractions of independent elements, respectively, 0 <p3 <1, 0 <q3 <1, 0 <r3 <1, 0 <s1 <1, p3 + q3 +r3+s1=1) and the like) and the like, and any one or two or more of these compounds may be included.

Among them, in that the capacity characteristics and stability of the battery can be improved, the lithium composite metal oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (eg, Li(Ni _0.6 Mn _0.2 Co _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 (eg, LiNi _0.8 Co _0.15 Al _0.05 O ₂ etc.), etc. In consideration of the significant 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(Ni _0.85 Mn _0.08 Co _0.05 Al _0.02 )O ₂ , and the like, these Any one or a mixture of two or more may be used.

In addition, the cathode active material may include a lithium composite transition metal oxide having a nickel content of 60 atm% or more of the total transition metal. For example, it may be 60atm% or more, 65atm% or more, 70atm% or more, 75atm% or more, 80atm% or more, 85atm% or more, or 90atm% or more.

The binder for the electrode is a component that assists in the bonding of the positive electrode active material and the electrode conductive material and the bonding to the current collector. Specifically, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene (PE) , polypropylene, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

The electrode conductive material is a component for further improving the conductivity of the cathode active material. The electrode conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon nanotubes; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used. Specific examples of commercially available conductive materials include Chevron Chemical Company (Chevron Chemical Company), Denka Black (Denka Singapore Private Limited), Gulf Oil Company products, etc.), Ketjenblack, and EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (Timcal).

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 including the cathode active material, and optionally a binder for a cathode and a cathode conductive material. there is.

(2) Cathode

In addition, the negative electrode may be prepared by coating a negative electrode active material slurry including a negative electrode active material, an electrode binder, an electrode conductive material, and a solvent on a negative electrode current collector. Meanwhile, the negative electrode may use a metal negative current collector itself as an electrode.

The anode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel A surface treated with carbon, nickel, titanium, silver, or the like, an aluminum-cadmium alloy, or the like may be used. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

Examples of the anode active material include natural graphite, artificial graphite, and carbonaceous materials; lithium-containing titanium composite oxide (LTO), metals (Me) that are Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; alloys composed of the metals (Me); an oxide (MeOx) of the metal (Me); and at least one negative electrode active material selected from the group consisting of a composite of the metal (Me) and carbon.

Since the contents of the binder for the electrode, the electrode conductive material, and the solvent are the same as those described above, a detailed description thereof will be omitted.

(3) Separator

As the separator, a conventional porous polymer film conventionally used as a separator, for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer A porous polymer film made of a polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used, but is not limited thereto. no.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are provided to more easily understand the present invention, but the present invention is not limited thereto.

Example

Example 1

After preparing Li(Ni _0.85 Mn _0.08 Co _0.05 Al _0.02 )O ₂ as a cathode active material, carbon black as a conductive material, and PVDF as a binder in a weight ratio of 97.6:1.2:1.2 (anode active material:conductive material:binder), N-methyl A positive electrode active material slurry was prepared by mixing in a pyrrolidone solvent. After applying the prepared cathode active material slurry to one side of an aluminum current collector (15㎛) (loading amount: 0.40-0.55 mg/25cm2), drying at 130 ° C for more than 20 minutes, 1-2 times to achieve a porosity of 24% A positive electrode was prepared by rolling.

An electrode in which natural graphite and artificial graphite were mixed at a ratio of 2:8 was used as the negative electrode, and an electrode assembly was prepared by interposing a porous polyethylene separator between the positive electrode and the negative electrode. After placing the electrode assembly inside the battery case, a lithium secondary battery was manufactured by injecting an electrolyte into the case. At this time, the electrolyte solution is 1M concentration of lithium hexafluorophosphate (LiPF ₆ ) dissolved in an organic solvent consisting of ethylene carbonate / ethylmethyl carbonate (mixed volume ratio of EC / EMC = 3/7), and 0.5% by weight of vinylene It was prepared by adding carbonate (VC), 0.5% by weight of propane sultone (PS) and 1% by weight of ethylene sulfate (ESa), and additionally adding 0.5% by weight of a phosphoric acid-based additive in which R in Formula 1 is all F.

Example 2

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

Example 3

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

Example 4

A lithium secondary battery was manufactured in the same manner as in Example 2, except for using a phosphoric acid-based additive in which R in Formula 1 is all CF ₃ in the electrolyte solution.

Example 5

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

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that the phosphoric acid-based additive was not added to the electrolyte.

Experimental example

Experimental Example: High Temperature Performance Measurement

The lithium secondary batteries prepared in Examples 1 to 5 and Comparative Example 1 were fully charged to 100% (2000 mAh) of SOC under a voltage condition of 4.2 V. Thereafter, after storage at a high temperature in a constant temperature chamber at 60 ° C. for 8 weeks, the capacity retention rate (%), resistance retention rate (%) and volume increase rate (%) were measured, and are shown in Table 1 below.

Capacity retention rate (%) Resistance retention rate (%) Volume increase rate (%) Example 1 (R=F, 0.5% by weight) 77.1 21.7 15.6 Example 2 (R=F, 1% by weight) 82.9 16.1 9.0 Example 3 (R=F, 3% by weight) 88.8 11.7 9.6 Example 4 (R=CF ₃ , 1% by weight) 80.3 19.6 11.2 Example 5 (R=F, 5% by weight) 69.1 38.6 10.5 Comparative Example 1 (no additives) 55.4 87.2 31.1

* Capacity retention rate (%): PNEsolution, using PEBC0506, charging with CC/CV (0.33C CC/ 4.2V 0.05C Current-cut CV) after 30 minutes of rest, discharging with CC (0.33) 3 times, and then 3 The second discharge capacity was reflected as capacity.

Capacity retention rate (%) = (N parking capacity) / (initial capacity) × 100

* Resistance retention rate (%): Using PEBC0506 from PNEsolution, after setting SOC 　50 based on discharge capacity, resistance was measured during CC pulse discharge with a current of 2.5C.

Resistance = (Voltage difference before and after discharge pulse)/(Current during discharge)

Resistance increase rate (%) = (N parking resistance - initial resistance) / (initial resistance) × 100

* Volume increase rate (%): Using TWD-PLS, TWD-150DM, the initial volume was measured after setting at SOC 100 before high temperature storage, and the volume was measured after cooling at room temperature immediately after high temperature storage.

Volume increase rate (%) = (Volume at week N - Initial volume) / (Initial volume) × 100

According to Table 1, the lithium secondary batteries (Examples 1 to 5) in which the phosphoric acid-based additive according to the present invention was added to the electrolyte not only had a high capacity retention rate even after storage at a high temperature, but also had a low resistance retention rate and a low volume increase rate, so that the phosphoric acid-based additive It can be seen that the high-temperature stability is significantly improved compared to the lithium secondary battery (Comparative Example 1) not added to the electrolyte.

All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

Claims (10)

A non-aqueous electrolyte solution for a lithium secondary battery comprising a lithium salt, an organic solvent, and a phosphoric acid-based additive represented by Formula 1 below.
[Formula 1]

In Formula 1,
R is a functional group that helps film formation, and is a functional group having a chain or cyclic structure containing at least one element selected from H, C, N, O, F, P, S, and Si. According to claim 1,
Wherein R is, the same as or different from each other, and each independently hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted mercapto, substituted or unsubstituted carbamoyl, substituted or unsubstituted Unsubstituted C _1-7 alkyl, substituted or unsubstituted C _1-7 halogenated alkyl, 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 al Kenyloxy, 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 A group consisting of alkylcarbonyl, substituted or unsubstituted C _1-4 alkoxycarbonyl, substituted or unsubstituted C _2-4 alkenyloxycarbonyl, and substituted or unsubstituted C _2-4 alkynyloxycarbonyl A non-aqueous electrolyte solution for a lithium secondary battery, characterized in that selected from. According to claim 2,
Wherein R is the same as or different from each other, and each independently represents hydrogen, halogen, hydroxy, cyano, nitro, substituted or unsubstituted amino, substituted or unsubstituted C _1-4 alkyl, substituted or unsubstituted C _{1- 4} halogenated alkyl, substituted or unsubstituted C _2-4 alkenyl, and substituted or unsubstituted C _2-4 alkynyl, substituted or unsubstituted C _1-4 alkoxy, substituted or unsubstituted mono- or di- A non-aqueous electrolyte solution for a lithium secondary battery, characterized in that it is selected from the group consisting of C _1-4 alkylamino, substituted or unsubstituted C _1-4 alkylcarbonyl, _and substituted or unsubstituted C 1-4 alkoxycarbonyl. According to claim 3,
wherein R is the same as or different from each other, and each independently hydrogen, halogen, substituted or unsubstituted C _1-4 alkyl, substituted or unsubstituted C _1-4 halogenated alkyl, and substituted or unsubstituted C _2-4 alkyl A non-aqueous electrolyte solution for a lithium secondary battery, characterized in that it is selected from the group consisting of kenyl. According to claim 1,
A non-aqueous electrolyte solution for a lithium secondary battery, characterized in that the phosphoric acid additive comprises 0.01% to 10% by weight based on the total weight of the electrolyte solution. According to claim 1,
The lithium salt is 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, LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₂ CF ₃ ) ₂ and LiN(SO ₂ CF ₃ ) ₂ ratio for a lithium secondary battery, characterized in that selected from the group consisting of water-based electrolyte. According to claim 1,
A non-aqueous electrolyte solution for a lithium secondary battery, characterized in that the concentration of the lithium salt is 0.1M to 3M. According to claim 1,
A non-aqueous electrolyte solution for a lithium secondary battery, characterized in that the organic solvent comprises at least one selected from the group consisting of ether, ester, amide, linear carbonate, and cyclic carbonate. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte for a lithium secondary battery according to any one of claims 1 to 8. According to claim 9,
The lithium secondary battery, characterized in that the positive electrode includes a lithium composite transition metal oxide having a layered structure as a positive electrode active material and having a nickel content of 60 atm% or more among the total transition metals.