KR102353962B1 - Electrolyte for Lithium Secondary Battery and Lithium Secondary Battery Containing the Same - Google Patents

Abstract

The present invention provides a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, and the secondary battery electrolyte of the present invention has very excellent high-temperature stability, low-temperature discharge capacity and lifespan characteristics.

Description

Lithium secondary battery electrolyte and lithium secondary battery containing same

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery containing the same, and more particularly, to a lithium secondary battery electrolyte containing a phosphine oxide derivative and a lithium secondary battery including the same.

Recently, as portable electronic devices have been widely distributed and reduced in size, thin film and light weight, research on enabling secondary batteries used as power sources to be small, lightweight and capable of charging and discharging for a long time is active.

A lithium secondary battery generates electrical energy by oxidation and reduction reactions when lithium ions are inserted and desorbed from the positive electrode and the negative electrode, and a material capable of inserting and deintercalating lithium ions is used as the negative electrode and the positive electrode, and the positive electrode It is prepared by filling an organic electrolyte or a polymer electrolyte between the cathode and the anode.

Organic electrolytes currently widely used include ethylene carbonate, propylene carbonate, dimethoxyethane, gamma butyrolactone, N,N-dimethylformamide, tetrahydrofuran, or acetonitrile. However, these organic electrolytes are generally easy to volatilize and have high flammability, so that when applied to a lithium ion secondary battery, there is a problem in safety at high temperature, such as causing ignition due to internal short circuit during internal heat generation due to overcharging or overdischarging.

In addition, during initial charging, lithium ions from lithium metal oxide, the positive electrode, move to the carbon electrode, which is the negative electrode, and intercalate with carbon. At this time, lithium has a strong reactivity, so the surface of the carbon particles, which is the negative electrode active material, and the electrolyte react. While doing so, a film called a solid electrolyte interface (SEI) film is formed on the surface of the anode.

The performance of the lithium secondary battery is greatly influenced by the composition of the organic electrolyte and the SEI film formed by the reaction between the organic electrolyte and the electrode.

That is, the formed SEI film suppresses a side reaction between the carbon material and the electrolyte solvent, for example, the decomposition of the electrolyte on the surface of carbon particles, which is the negative electrode, and prevents the collapse of the negative electrode material due to co-intercalation of the electrolyte solvent into the negative electrode material. In addition to this, the performance degradation of the battery is minimized by faithfully performing the role of the conventional lithium ion tunnel.

Therefore, in order to solve the above problems, various studies are being attempted to develop a new organic electrolyte containing an additive.

For example, Japanese Patent JP2002-260725 discloses a non-aqueous lithium ion battery capable of preventing overcharge current and thermal runaway by using an aromatic compound such as biphenyl. In addition, in U.S. Patent No. 5,879,834, a small amount of aromatic compounds such as biphenyl and 3-chlorothiophene are added to improve battery safety by electrochemically polymerizing under abnormal overvoltage conditions to increase internal resistance. A method for this is described.

However, research is required to improve safety at high and low temperatures while still having a high capacity retention rate.

Japanese Patent JP2002-260725 U.S. Patent No. 5,879,834

The present invention provides a lithium secondary battery electrolyte having excellent high-temperature and low-temperature characteristics while maintaining good basic performance such as high-rate charge/discharge characteristics and lifespan characteristics, and a lithium secondary battery including the same.

The present invention provides a lithium secondary battery electrolyte, the lithium secondary battery electrolyte of the present invention,

lithium salt;

non-aqueous organic solvents; and

and a phosphine oxide derivative represented by the following formula (1).

[Formula 1]

(In Formula 1,

R ¹ to R ² are each independently (C6-C12)aryl, (C3-C12)heteroaryl or (C1-C10)alkyl(C6-C12)aryl;

이며;R is independently of each other hydrogen, (C6-C12)aryl, (C3-C12)heteroaryl or

is;

A is a single bond or -(CR ³ R ⁴ ) _n -, R ³ to R ⁴ are each independently hydrogen or (C1-C10)alkyl, and n is an integer from 1 to 4.)

Preferably, in Formula 1 according to an embodiment of the present invention, R ¹ to R ² may be each independently (C6-C12)aryl.

이며; A는 단일결합 또는 -(CR³R⁴)_n-이며, R³ 내지 R⁴는 서로 독립적으로 수소이며, n은 1 내지 2의 정수일 수 있다.Preferably, in Formula 1 according to an embodiment of the present invention, R is independently of each other hydrogen or

is; A is a single bond or -(CR ³ R ⁴ ) _n -, R ³ to R ⁴ are each independently hydrogen, and n may be an integer of 1 to 2.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, Chemical Formula 1 may be selected from the following structures, but is not limited thereto.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the phosphine oxide derivative represented by Formula 1 may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the electrolyte is one or two selected from the group consisting of an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group-containing compound It may further include the above additives.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the electrolyte includes lithium difluoro oxalatoborate (LiFOB), lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate , ethane sultone, propane sulton (PS), butane sulton (butane sulton), ethene sultone, butene sultone, and may further include an additive selected from the group consisting of propene sultone (PRS).

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the additive may be included in an amount of 0.1% to 5.0% by weight based on the total weight of the electrolyte.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent may be selected from a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a mixed solvent thereof, and the cyclic carbonate is ethylene carbonate, propylene carbonate , butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, and may be selected from the group consisting of mixtures thereof, the linear carbonate is dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl It may be selected from the group consisting of carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and mixtures thereof.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent may have a mixing volume ratio of the linear carbonate solvent: the cyclic carbonate solvent of 1 to 9: 1.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the lithium salt is LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO _{2 )} ) ₂ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ₆ H ₅ SO ₃ , LiSCN, LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI and LiB(C ₂ O ₄ ) ₂ One selected from the group consisting of or two or more.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the lithium salt may be present in a concentration of 0.1 to 2.0 M.

In addition, the present invention provides a lithium secondary battery comprising the lithium secondary battery electrolyte according to the present invention.

The lithium secondary battery electrolyte according to the present invention includes the phosphine oxide derivative represented by Chemical Formula 1, so that swelling of the battery at a high temperature is remarkably improved and has excellent high-temperature storage characteristics.

In addition, the lithium secondary battery electrolyte according to the present invention necessarily contains a phosphine oxide derivative represented by Formula 1, wherein one of the substituents of P of the phosphine oxide is a functional group including a vinyl group, and the other two are aromatic ring compounds. By doing so, not only the capacity recovery rate at high temperatures but also the discharge capacity at low temperatures can be remarkably increased.

In addition, the lithium secondary battery electrolyte according to the present invention is a phosphine oxide derivative represented by Formula 1 of the present invention, an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group-containing compound. By further including one or two or more additives selected from, it has better lifespan characteristics, high temperature stability and low temperature characteristics.

In addition, the lithium secondary battery of the present invention has excellent high-temperature storage stability and low-temperature characteristics while maintaining good basic performance such as high-efficiency charge/discharge characteristics and lifespan characteristics by employing the lithium secondary battery electrolyte of the present invention containing a phosphine oxide derivative. .

Hereinafter, the present invention will be described in more detail. If there is no other definition in the technical and scientific terms used at this time, it has the meaning commonly understood by those of ordinary skill in the art to which this invention belongs, and in the following description, it may unnecessarily obscure the subject matter of the present invention. A description of possible known functions and configurations will be omitted.

The present invention relates to an electrolyte solution for a lithium secondary battery for providing a battery having high high temperature storage characteristics and high lifespan characteristics and excellent discharge capacity at low temperature.

The present invention is a lithium salt; non-aqueous organic solvents; And a phosphine oxide derivative represented by the following formula (1); provides a lithium secondary battery electrolyte comprising:

[Formula 1]

(In Formula 1,

R ¹ to R ² are each independently (C6-C12)aryl, (C3-C12)heteroaryl or (C1-C10)alkyl(C6-C12)aryl;

이며;R is independently of each other hydrogen, (C6-C12)aryl, (C3-C12)heteroaryl or

is;

A is a single bond or -(CR ³ R ⁴ ) _n -, R ³ to R ⁴ are each independently hydrogen or (C1-C10)alkyl, and n is an integer from 1 to 4.)

The secondary battery electrolyte of the present invention contains a phosphine oxide derivative, specifically, the phosphine oxide derivative represented by Chemical Formula 1, so that the capacity recovery rate at high temperature is high, and the thickness change rate is low, so it is more stable at high temperature.

More specifically, in the phosphine oxide derivative represented by Formula 1 of the present invention, P of the phosphine oxide is substituted with a functional group containing a vinyl group and the other two are substituted with an aromatic ring (aryl, heteroaryl or alkylaryl). Although chemically stable by having a specific structure, a lithium secondary battery including the same can improve high-temperature and low-temperature characteristics.

In terms of chemical stability and electrical properties, preferably in the lithium secondary battery electrolyte according to an embodiment of the present invention, in Formula 1, preferably R ¹ to R ² may each independently be (C6-C12)aryl.

이며; A는 단일결합 또는 -(CR³R⁴)_n-이며, R³ 내지 R⁴는 서로 독립적으로 수소이며, n은 1 내지 2의 정수일 수 있다.More preferably, in Formula 1 according to an embodiment of the present invention, R ¹ to R ² are each independently (C6-C12)aryl, and R are each independently hydrogen or

is; A is a single bond or -(CR ³ R ⁴ ) _n -, R ³ to R ⁴ are each independently hydrogen, and n may be an integer of 1 to 2.

More specifically, the phosphine oxide derivative of the present invention may be selected from the following structures, but is not limited thereto:

The substituents containing "alkyl" and other "alkyl" moieties described in the present invention include both straight-chain or pulverized forms, and have 1 to 10 carbon atoms, preferably 1 to 6, more preferably 1 to 4 carbon atoms. have a ruler

In addition, the "aryl" described in the present invention is an organic radical derived from an aromatic hydrocarbon by removal of one hydrogen, and is preferably a single or fused group containing 4 to 7, preferably 5 or 6 ring atoms in each ring. It includes a ring system, and includes a form in which a plurality of aryls are connected by a single bond. Specific examples include, but are not limited to, phenyl, naphthyl, biphenyl, anthryl, indenyl, fluorenyl, and the like.

The "heteroaryl" described in the present invention includes 1 to 4 heteroatoms selected from B, N, O, S, P (=O), Si and P as aromatic ring skeleton atoms, and the remaining aromatic ring skeleton atoms are carbon Phosphorus refers to an aryl group, which is a 5- to 6-membered monocyclic heteroaryl, and a polycyclic heteroaryl condensed with one or more benzene rings, and may be partially saturated. In addition, heteroaryl in the present invention includes a form in which one or more heteroaryl is connected by a single bond.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the phosphine oxide derivative of Formula 1 may be included in an amount of 0.1 to 5% by weight based on the total weight of the secondary battery electrolyte, and more preferably 1 in terms of high temperature stability. to 3% by weight. When the content of the phosphine oxide derivative of Formula 1 is less than 0.1% by weight, there is no additive effect such as low high-temperature stability or insignificant improvement in capacity retention, and the effect of improving discharge capacity or output of the lithium secondary battery is insignificant, , when more than 5% by weight is included, such as rapid life deterioration occurs, rather the characteristics of the lithium secondary battery is lowered.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the electrolyte is a lifespan improving additive for improving battery life, and an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group One or two or more additives selected from the group consisting of containing compounds may be further included.

The oxalatoborate-based compound may be a compound represented by the following Chemical Formula 11 or lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB).

[Formula 11]

(In Formula 11, R ₁₁ and R ₁₂ are each independently a halogen atom or a C1 to C10 alkyl group substituted with one or more halogens.)

Specific examples of the oxalatoborate-based additive include LiB(C ₂ O ₄ )F ₂ (lithium difluoro oxalatoborate, LiFOB) or LiB(C ₂ O ₄ ) ₂ (lithium bisoxalatoborate, LiBOB). can be heard

The fluorine-substituted carbonate-based compound may be fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), fluorodimethyl carbonate (FDMC), fluoroethylmethyl carbonate (FEMC), or a combination thereof.

The vinylidene carbonate-based compound may be vinylene carbonate (VC), vinyl ethylene carbonate (VEC), or a mixture thereof.

The sulfinyl group (S=O)-containing compound may be sulfone, sulfite, sulfonate and sultone (cyclic sulfonate), and these may be used alone or in combination. Specifically, the sulfone may be represented by the following Chemical Formula 12, and may be divinyl sulfone. The sulfite may be represented by the following Chemical Formula 13, and may be ethylene sulfite or propylene sulfite. The sulfonate may be represented by the following Chemical Formula 14, and may be diallyl sulfonate. In addition, non-limiting examples of sultone include ethane sultone, propane sulton, butane sulton, ethene sultone, butene sultone, propene sultone, and the like.

[Formula 12]

[Formula 13]

[Formula 14]

(In Formulas 12, 13, and 14, R ₁₃ and R ₁₄ are each independently hydrogen, a halogen atom, a C1-C10 alkyl group, a C2-C10 alkenyl group, a halogen-substituted C1-C10 alkyl group, or a halogen It is a substituted C2-C10 alkenyl group.)

In the lithium secondary battery electrolyte according to an embodiment of the present invention, more preferably, the electrolyte is lithium difluoro oxalatoborate (LiFOB), lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), fluorine Roethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate ( diallyl sulfonate), ethane sultone, propane sulton (PS), butane sulton, ethene sultone, butene sultone and propene sultone (PRS) may further include an additive selected from the group consisting of, more preferably Lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfite, ethane sultone, propane sulton , PS) may further include one or two or more additives selected from.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the content of the additive is not particularly limited, but in order to improve battery life in the secondary battery electrolyte, 0.1 to 5% by weight based on the total weight of the electrolyte, more preferably For example, it may be included in an amount of 0.1 to 3% by weight.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent may include carbonate, ester, ether, or ketone alone or a mixed solvent thereof, but a cyclic carbonate-based solvent, a linear carbonate-based solvent, and It is preferably selected from these mixed solvents, and it is most preferable to use a mixture of a cyclic carbonate-based solvent and a linear carbonate-based solvent. The cyclic carbonate solvent has a large polarity and can sufficiently dissociate lithium ions, but has a disadvantage in that the ionic conductivity is small due to a large viscosity. Therefore, the characteristics of the lithium secondary battery can be optimized by mixing the cyclic carbonate solvent with a linear carbonate solvent having a low polarity but low viscosity.

The cyclic carbonate-based solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, and mixtures thereof, and the linear carbonate-based solvent is dimethyl carbonate, It may be selected from the group consisting of diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and mixtures thereof.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent is a mixed solvent of a cyclic carbonate-based solvent and a linear carbonate-based solvent, and a mixing volume ratio of the linear carbonate solvent: the cyclic carbonate solvent is 1 to 9: 1 may be used, preferably mixed in a volume ratio of 1.5 to 4:1.

In the high voltage lithium secondary battery electrolyte according to an embodiment of the present invention, the lithium salt is not limited, but LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ₆ H ₅ SO ₃ , LiSCN, LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI and LiB(C ₂ O ₄ ) ₂ as It may be one or two or more selected from the group consisting of.

The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M, more preferably used within the range of 0.7 to 1.6 M. If the concentration of the lithium salt is less than 0.1 M, the conductivity of the electrolyte is lowered to deteriorate the electrolyte performance, and when the concentration of the lithium salt exceeds 2.0 M, the viscosity of the electrolyte increases and the mobility of lithium ions decreases. The lithium salt serves as a source of lithium ions in the battery to enable the basic operation of the lithium secondary battery.

The lithium secondary battery electrolyte of the present invention is generally stable in a temperature range of -20 ° C to 60 ° C, and maintains electrochemically stable characteristics even at a voltage of 4.4 V, so it can be applied to all lithium secondary batteries such as lithium ion batteries and lithium polymer batteries. can

In addition, the present invention provides a lithium secondary battery comprising the lithium secondary battery electrolyte.

Non-limiting examples of the secondary battery include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The lithium secondary battery prepared from the lithium secondary battery electrolyte according to the present invention exhibits a high temperature storage efficiency of 70% or more, and at the same time, the thickness increase rate of the battery when left at a high temperature for a long period of time is very low, preferably 1 to 15%, rather than 1 to 20% characterized in that

The lithium secondary battery of the present invention includes a positive electrode and a negative electrode.

The positive electrode includes a positive electrode active material capable of intercalating and deintercalating lithium ions, and the positive electrode active material is preferably a composite metal oxide with at least one selected from cobalt, manganese, and nickel and lithium. The solid solution ratio between metals can be made variously, and in addition to these metals, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, An element selected from the group consisting of Sr, V and rare earth elements may be further included. As a specific example of the positive active material, a compound represented by any one of the following formulas may be used:

Li _a A _1-b B _b D ₂ (wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li _a E _1-b B _b O _2-c D _c (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _2-b B _b O _4-c D _c (wherein 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); and LiFePO ₄ .

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y or a combination thereof; J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

The negative electrode includes an anode active material capable of occluding and deintercalating lithium ions, and as such a negative active material, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, lithium metal, an alloy of lithium and other elements, etc. may be used. can For example, the amorphous carbon includes hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1500° C. or lower, mesophase pitch-based carbon fiber (MPCF), and the like. As crystalline carbon, there are graphite-based materials, specifically natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, and the like. The carbon material is preferably a material having an interplanar distance of 3.35 to 3.38 Å, and a crystallite size (Lc) of at least 20 nm by X-ray diffraction. As another element alloying with lithium, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium may be used.

The positive electrode or negative electrode may be prepared by dispersing an electrode active material, a binder and a conductive material, and, if necessary, a thickener in a solvent to prepare an electrode slurry composition, and applying the slurry composition to an electrode current collector. As the positive electrode current collector, aluminum or an aluminum alloy may be commonly used, and as the negative electrode current collector, copper or a copper alloy may be commonly used. The positive electrode current collector and the negative electrode current collector may be in the form of a foil or a mesh.

The binder is a material that acts as a paste of the active material, mutual adhesion of the active material, adhesion to the current collector, and a buffer effect against expansion and contraction of the active material, for example, polyvinylidene fluoride (PVdF), polyhexafluoro Propylene-polyvinylidene fluoride copolymer (PVdF/HFP)), poly(vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly(methyl meta) acrylate), poly(ethyl acrylate), polytetrafluoroethylene, polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, and acrylonitrile-butadiene rubber. The content of the binder is 0.1 to 30% by weight, preferably 1 to 10% by weight based on the electrode active material. When the content of the binder is too small, the adhesive force between the electrode active material and the current collector is insufficient, and when the content of the binder is too large, the adhesive strength is improved, but the content of the electrode active material is reduced by that much, which is disadvantageous in increasing the battery capacity.

The conductive material is used to impart conductivity to the electrode. In the battery, any material that does not cause chemical change and is electronically conductive can be used. Graphite-based conductive agent, carbon black-based conductive agent, metal or metal compound-based conductive material At least one selected from the group consisting of conductive agents may be used. Examples of the graphite-based conductive agent include artificial graphite, natural graphite, and the like, and examples of the carbon black-based conductive agent include acetylene black, ketjen black, denka black, thermal black, and channel black. (channel black), etc., and examples of the metal-based or metal compound-based conductive agent include perovskite such as _{tin, tin oxide, tin phosphate (SnPO 4} ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO _{3 .} there is material However, it is not limited to the conductive agents listed above.

The content of the conductive agent is preferably 0.1 to 10% by weight based on the electrode active material. When the content of the conductive agent is less than 0.1% by weight, the electrochemical properties are deteriorated, and when it exceeds 10% by weight, the energy density per weight is reduced.

The thickener is not particularly limited as long as it can play a role in controlling the viscosity of the active material slurry, but for example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. may be used.

A non-aqueous solvent or an aqueous solvent is used as a solvent in which the electrode active material, binder, conductive material, etc. are dispersed. Examples of the nonaqueous solvent include N-methyl-2-pyrroldidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran.

The lithium secondary battery of the present invention may include a separator that prevents a short circuit between the positive electrode and the negative electrode and provides a passage for lithium ions, such as polypropylene, polyethylene, polyethylene/polypropylene, polyethylene/polypropylene/ Polyolefin-based polymer membranes such as polyethylene, polypropylene/polyethylene/polypropylene, or multiple membranes thereof, microporous films, woven fabrics and nonwoven fabrics may be used. In addition, a film coated with a resin having excellent stability on the porous polyolefin film may be used.

The lithium secondary battery of the present invention may be formed in other shapes such as a cylindrical shape or a pouch shape in addition to the prismatic shape.

Hereinafter, Examples and Comparative Examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto. It is considered that all lithium salts are dissociated so that the lithium ion concentration becomes 1 mole (1M), and a lithium salt _{such as LiPF 6} can be dissolved in the base solvent so that the concentration becomes 1 mole (1M) to form a base electrolyte. .

[Example 1] Synthesis of 2,3-di(bis(phenylphosphinyl))buta-1,3-diene hereinafter referred to as 'PEA64')

30 mL of THF and 10.5 mL of chlorodiphenylphosphine were added to the reactor and cooled to ^{0 o C.} 2.27 g of 2-butin-l,4-diol was dissolved in 5 mL of pyridine and 30 mL of THF, added very slowly, and then heated to room temperature and stirred. When the reaction was completed, _{40 mL of H 2} O was added to stop the reaction, and _{200 mL of CH 2} Cl ₂ was used for extraction. After extracting the aqueous layer with _{200 mL of CH 2} Cl ₂ once more, the oil layers were collected and sat. It was washed with _{NaHCO 3 aqueous solution.} The oil layers were collected _{, dried over Na 2} SO ₄ , filtered, and distilled under reduced pressure. Recrystallization using diethyl ether and THF gave the title compound, 10.2 g.

¹ H NMR (400 MHz, CDCl ₃ ): δ = 5.53 (d, 2H, C=CHH, J(HP)=20 Hz), 6.63 (d, 2H, C=CHH, J(HP)=42 Hz) , 7.40-7.80 (m, 20H, arom.).

[Example 2] Synthesis of allyldiphenylphosphine oxide (hereinafter referred to as 'PEA72')

5 g of diphenylphosphine oxide was put into a reactor, 50 mL of THF was added, and then cooled and stirred at ^{0 o C.} 1.28 g of 60% NaH was divided into 5 portions and slowly added, followed by ^{stirring at 0 o} C for 3 hours. After slowly adding 3.2 mL of allyl bromide, the temperature was raised to reflux conditions and stirred for 6 hours. When the reaction was completed, the reaction was terminated ^{by cooling to 0 o} C, and slowly adding 50 mL of 0.5 M HCl aqueous solution. 100 mL of ethyl acetate was added to extract, and the aqueous layer was extracted once more with 100 mL of ethyl acetate. The oil layers were collected, washed with Brine _{, dried over Na 2} SO ₄ , filtered, and concentrated under reduced pressure. Purification by column chromatography gave the title compound, 2.3 g.

¹ H NMR (400 MHz, CDCl ₃ ): δ = 7.76-7.63 (m, 4H), 7.47-7.03 (m, 6 H), 5.83-6.63 (m, 1H), 5.15-5.04 (m, 2H), 3.15-3.04 ppm (dd, J=14.5, 7.33 Hz, 2H).

[Comparative Example 1] Synthesis of diethyl allylphosphonate (hereinafter referred to as 'PEA86')

20 mL of triethylphosphite and 11 mL of allyl bromide were put into a reactor, the ^{temperature was raised to 140 o} C, and the mixture was stirred for 4 hours. Remaining allyl bromide was removed by distillation under reduced pressure, and column chromatography was performed to obtain the title compound, 21 g.

¹ H NMR (400 MHz, CDCl ₃ ): δ = 5.92-5.70 (m, 1H), 5.35-5.12 (m, 2H), 4.20-4.06 (m, 4H), 2.64 (m, 2H), 1.34 (t) , 6H)

[Example 3-9 and Comparative Example 2-4]

Electrolyte solution is ethylene carbonate (EC): ethyl methyl carbonate (EMC) a 3:07 volume ratio of the solution obtained by dissolving to a 1.0 M solution of LiPF ₆ in a mixed solvent base electrolytic solution (1M in of LiPF _6, EC / EMC = 3 : 7) and was prepared by additionally adding the components listed in Table 1 below.

A battery to which the non-aqueous electrolyte is to be applied was prepared as follows.

_{LiNiCoMnO 2} and LiMn ₂ O ₄ as a cathode active material were mixed in a weight ratio of 1:1, polyvinylidene fluoride (PVdF) as a binder and carbon as a conductive agent were mixed in a weight ratio of 92:4:4, and then N- A positive electrode slurry was prepared by dispersing in methyl-2-pyrrolidone. The slurry was coated on an aluminum foil having a thickness of 20 μm, dried and rolled to prepare a positive electrode. An anode active material slurry was prepared by mixing artificial graphite as an anode active material, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener in a weight ratio of 96:2:2, and then dispersing it in water. This slurry was coated on copper foil having a thickness of 15 μm, dried and rolled to prepare a negative electrode.

A cell was constructed using a pouch having a size of 8 mm thick x 270 mm x 185 mm thick by stacking a 25 μm thick polyethylene (PE) film separator between the prepared electrodes. , a 25Ah class lithium secondary battery for EV was prepared by injecting the non-aqueous electrolyte.

The performance of the 25Ah class battery for EV manufactured in this way was evaluated as follows. Evaluation items are as follows.

*Evaluation items*

1. -20℃ 1C discharge capacity: After charging at room temperature at 25A, 4.2V CC-CV for 3 hours, and leaving it at -20℃ for 4 hours, after discharging at a current of 25A and CC to 2.7V, the usable capacity compared to the initial capacity (%) was measured.

2. Capacity recovery rate for 30 days at 60℃: After 3 hours of charging at room temperature with 4.2V, 25A CC-CV, and left at 60℃ for 30 days, after discharging at a current of 25A and CC to 2.7V, the recovery rate compared to the initial capacity (%) was measured.

3. Thickness increase rate after 30 days at 60℃: After charging for 3 hours at 4.4V, 12.5A CC-CV at room temperature, the thickness of the battery is called A, and 30 at 60℃ and atmospheric pressure exposed to the atmosphere using a sealed thermostat. When the thickness of the battery left unattended is B, the increase rate of the thickness was calculated as in Equation 1 below.

[Equation 1]

(B-A)/A × 100(%)

4. Room temperature life: After charging for 3 hours at 4.2V, 50A CC-CV at room temperature, discharge to 2.7V at 2.7V and 25A is repeated 500 times. In this case, the first discharge capacity was referred to as C, and the capacity retention rate during the lifetime was calculated by dividing the 300th discharge capacity by the first discharge capacity.

Electrolyte composition 60℃ after 30 days Capacity retention over life -20℃ discharge
Volume capacity recovery rate thickness increase rate Example 3 Basic electrolyte + PEA64 1wt% 78% 10% 75% 80% Example 4 Basic electrolyte + PEA72 1wt% 80% 8% 78% 83% Example 5 Basic electrolyte + PEA72 0.5wt% 75% 12% 71% 78% Example 6 Basic electrolyte + PEA72 3wt% 83% 6% 76% 72% Example 7 Basic electrolyte + PEA72 1wt% + VC 1wt% 86% 9% 84% 80% Example 8 Basic electrolyte+PEA72 1wt% +VC 1wt% +PS 1wt% 89% 5% 89% 78% Example 9 Basic electrolyte+PEA72 1wt%+VC 1wt%+LiBOB 1wt% 88% 6% 91% 85% Comparative Example 2 basic electrolyte 37% 30% 20% 55% Comparative Example 3 Basic electrolyte + PEA86 1wt% 39% 35% 23% 50% Comparative Example 4 Basic electrolyte + PEA86 1wt%+VC 1wt% +PS 1wt% 45% 19% 45% 48% Basic electrolyte: 1M LiPF ₆ , EC/EMC=3:7

LiBOB: Lithium-bis(Oxalato)Borate
VC : Vinylene carbonate
PS: 1,3-propane sultone

As shown in Table 1, the lithium secondary battery containing the lithium secondary battery electrolyte according to the present invention showed a very high capacity recovery rate even after 30 days at 60°C, a very low thickness increase rate, a high discharge capacity at -20°C, and a high lifespan The medium capacity retention rate is also very high.

On the other hand, the lithium secondary battery employing the secondary battery electrolyte of Comparative Example 1 which does not contain the phosphine oxide derivative represented by Formula 1 of the present invention has a low high-temperature capacity recovery rate, and the thickness increase rate is also very high at 30%, which is very high. It can be seen that the stability is poor.

Moreover, it can be seen that Comparative Example 2 including PEA 86 having a structure different from that of the present invention as an additive also has low high-temperature stability and low low-temperature discharge capacity.

These results show that the specific structure of the phosphine oxide derivative represented by Formula 1 of the present invention, specifically, P of the phosphine oxide has a substituent including a vinyl group and two aromatic rings, and thus a lithium secondary battery employing the same It can be seen that the high-temperature stability and low-temperature discharge capacity of the

In addition, the secondary battery electrolyte of the present invention is a phosphine oxide derivative represented by Formula 1 of the present invention, lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), vinylene carbonate (VC), vinylethylene carbonate By further including one or more additives selected from (VEC), ethylene sulfite, ethane sultone, and propane sulton (PS), high-temperature storage stability, low-temperature discharge capacity and lifespan characteristics are further improved.

As described above, the embodiments of the present invention have been described in detail, but those of ordinary skill in the art to which the present invention pertains can view the present invention without departing from the spirit and scope of the present invention as defined in the appended claims. The invention may be practiced with various modifications. Accordingly, modifications of future embodiments of the present invention will not depart from the teachings of the present invention.

Claims (14)

lithium salt;
non-aqueous organic solvents; and
A secondary battery electrolyte comprising; a phosphine oxide derivative represented by the following formula (1).
[Formula 1]

(In Formula 1,
R ¹ to R ² are each independently (C6-C12)aryl, (C3-C12)heteroaryl or (C1-C10)alkyl(C6-C12)aryl;
R is

is;
A is a single bond or -(CR ³ R ⁴ ) _n -, R ³ to R ⁴ are each independently hydrogen or (C1-C10)alkyl, and n is an integer from 1 to 4.) The method of claim 1,
In Chemical Formula 1, R ¹ to R ² are each independently (C6-C12)aryl. 3. The method of claim 2,
A is a single bond or -(CR ³ R ⁴ ) _n -, R ³ to R ⁴ are each independently hydrogen, n is an integer of 1 to 2 secondary battery electrolyte. The method of claim 1,
Formula 1 is a secondary battery electrolyte that is selected from the following structure.

The method of claim 1,
The compound represented by Formula 1 is a secondary battery electrolyte that is included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte. The method of claim 1,
The electrolyte is an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a secondary battery electrolyte further comprising one or more additives selected from the group consisting of a sulfinyl group-containing compound. 7. The method of claim 6,
The additive is lithium difluoro oxalatoborate (LiFOB), lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate, ethane sultone, propane sulton (PS), butane A secondary battery electrolyte that is selected from the group consisting of sultone (butane sulton), ethene sultone, butene sultone and propene sultone (PS). 7. The method of claim 6,
The additive is a secondary battery electrolyte containing 0.1 to 5.0% by weight based on the total weight of the electrolyte. The method of claim 1,
The non-aqueous organic solvent is a secondary battery electrolyte selected from a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a mixed solvent thereof. 10. The method of claim 9,
The cyclic carbonate is selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, and mixtures thereof, and the linear carbonate is dimethyl carbonate, diethyl carbonate, dipropyl A secondary battery electrolyte selected from the group consisting of carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and mixtures thereof. 10. The method of claim 9,
The non-aqueous organic solvent is a linear carbonate solvent: a secondary battery electrolyte having a mixing volume ratio of 1 to 9: 1 of the cyclic carbonate solvent. The method of claim 1,
The lithium salt is LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ₆ H ₅ SO ₃ , LiSCN, LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI, and LiB(C ₂ O ₄ ) ₂ One or two or more secondary battery electrolytes selected from the group consisting of. The method of claim 1,
The lithium salt is present in a concentration of 0.1 to 2.0 M secondary battery electrolyte. A lithium secondary battery comprising the secondary battery electrolyte according to any one of claims 1 to 13.