KR102440658B1 - Electrolyte for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

본 발명의 리튬이차전지용 전해액을 이용한 리튬이차전지는 고온수명 특성이 우수하며, 고온저장시 내부저항(IR) 감소, 전지두께 팽창 억제 및 용량유지율이 월등하다.The present invention relates to a thiocarbonyl compound represented by the following formula (1); electrolyte additive;
lithium salt; and a non-aqueous organic solvent; and an electrolyte solution for a lithium secondary battery comprising the same, and a lithium secondary battery including the same.
[Formula 1]

The lithium secondary battery using the electrolyte solution for a lithium secondary battery of the present invention has excellent high-temperature life characteristics, and is excellent in reducing internal resistance (IR), suppressing battery thickness expansion, and maintaining capacity at high temperature storage.

Description

Electrolyte for lithium secondary battery and lithium secondary battery comprising same

The present invention relates to an electrolyte solution for a lithium secondary battery and a lithium secondary battery containing the same, and more particularly, lithium having excellent high-temperature life characteristics, reduced internal resistance (IR) during high-temperature storage, suppression of battery thickness expansion, and superior capacity retention It relates to an electrolyte for a secondary battery and a lithium secondary battery including the same.

As the field of application of rechargeable batteries is expanded to mobile phones, digital cameras, notebook computers and power tools, as well as electric bicycles, electric vehicles, and energy storage devices, high energy density of the rechargeable batteries used as power sources for energy electronic devices has been increased. And the demand for high safety is increasing.

A lithium secondary battery is a rechargeable battery that can best meet these needs, and research on it is being actively conducted. A lithium secondary battery is a negative electrode made of a carbon material capable of insertion and desorption of lithium ions, a positive electrode made of lithium-containing oxide, etc., a porous separator positioned between the negative electrode and the positive electrode, and injected between the negative electrode and the positive electrode, between the two electrodes It is composed of a non-aqueous electrolyte, a medium that allows lithium ions to move in

As the non-aqueous electrolyte, a material in which a lithium salt such as LiPF ₆ is dissolved in a non-aqueous organic solvent such as propylene carbonate, ethyl carbonate, dimethyl carbonate, and diethyl carbonate is used.

However, in general, when the non-aqueous organic solvent is stored at a high temperature for a long time, gas is generated due to the oxidation of the electrolyte, which may cause a problem in that the secondary battery is ignited and exploded.

Recently, in order to solve the problem of ignition and explosion of secondary batteries, various studies have been made to develop an electrolyte of a new composition including additives. However, in a secondary battery using a carbonate-based organic solvent, gas inside the secondary battery due to the decomposition of the carbonate-based organic solvent during the reaction of forming a solid electrolyte interphase film (SEI film), which is a solid electrolyte decomposition product accumulated on the surface of the anode. There is a problem that occurs. Examples of the gas include hydrogen gas (H ₂ ), carbon monoxide gas (CO), carbon dioxide gas (CO ₂ ), methane gas (CH ₄ ), and the like, depending on the type of the non-aqueous organic solvent and the anode active material.

Therefore, the thickness of the battery expands during charging due to the generation of the gases inside the secondary battery, and when the secondary battery is left at a high temperature in a fully charged state (for example, after charging 4.2 V 100% , 60 ℃ 4 weeks) The negative electrode passivation film (SEI film) slowly decays by the increased electrochemical energy and thermal energy over time, causing a side reaction in which the surrounding electrolyte continuously reacts with the newly exposed surface of the negative electrode. do. Due to such continuous gas generation, the internal pressure of the secondary battery increases, and the performance of the secondary battery is deteriorated, such as a decrease in the lifespan of the secondary battery at a high temperature due to volume expansion of the secondary battery.

In order to prevent such a decrease in the performance of the secondary battery, in order to improve the battery characteristics such as the life characteristics and storage characteristics of the lithium secondary battery, various studies on non-aqueous organic solvents and additives as electrolyte components are being made.

However, additives such as 1,3-propanesultone and 1,3-propensultone, which have been extensively studied as electrolyte additives in the prior art, improve the high-temperature storage characteristics of secondary batteries during long-term high-temperature storage, but high-temperature lifespan characteristics of secondary batteries. This diminishing problem arises.

Republic of Korea Patent Publication No. 2019-0022382

An object of the present invention is to provide an electrolyte for a lithium secondary battery capable of improving both high-temperature storage characteristics and high-temperature lifespan characteristics of secondary batteries, and a lithium secondary battery including the same, in order to solve the problems of the prior art.

The electrolyte for a lithium secondary battery according to an embodiment of the present invention is

a thiocarbonyl compound represented by the following formula (1);

electrolyte additive;

lithium salt; and

Non-aqueous organic solvent; includes.

[Formula 1]

(In Formula 1, R1 and R2 are the same or different from each other, and R1 is each independently hydrogen, deuterium, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or a substituted or unsubstituted ring by combining with an adjacent group to form a ring, and , R2 is each independently hydrogen, deuterium, C1-C6 alkyl group, C3-C6 cycloalkyl group)

In addition, the thiocarbonyl compound according to an embodiment of the present invention is O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate (Propargyl-1H-imidazole-1) represented by Formula 2 below. -thiocarboxylate).

[Formula 2]

The thiocarbonyl compound according to an embodiment of the present invention may be included in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte for a lithium secondary battery.

And, the electrolyte additive according to an embodiment of the present invention is lithium difluorophosphate (Lithium difluorophosphate), lithium tetrafluoro (oxaleto) phosphate (Lithium tetrafluoro (oxalate) phosphate, lithium bis (fluorosulfonyl) imide) (Lithium bis(fluorosulfonyl)imide), 1,3-propane sultone, 1,3-propene sultone, fluoroethylene carbonate, vinyl It may include at least one selected from the group consisting of ren carbonate (Vinylene Carbonate), and vinyl ethylene carbonate (Vinyl Ethylene Carbonate).

The electrolyte additive according to an embodiment of the present invention may be included in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte for a lithium secondary battery.

In addition, the lithium salt according to an embodiment of the present invention is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , at least 1 selected from the group consisting of LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , and LiB(C ₂ O ₄ ) ₂ . It may include more than one species.

The concentration of the lithium salt according to an embodiment of the present invention may be included in the range of 0.1 to 2.0 M (mol/L) with respect to the total amount of the electrolyte for a lithium secondary battery.

In addition, the non-aqueous organic solvent according to an embodiment of the present invention may be a linear carbonate-based solvent, a cyclic carbonate-based solvent, or a mixture thereof.

The linear carbonate-based solvent according to an embodiment of the present invention is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC) and methyl propyl carbonate (MPC) may include at least one selected from the group consisting of.

In addition, the cyclic carbonate-based solvent according to an embodiment of the present invention is ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), 2,3-butylene carbonate, 1,2- It may include at least one selected from the group consisting of pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

Here, in the mixed solvent of the linear carbonate-based solvent and the cyclic carbonate-based solvent according to an embodiment of the present invention, the linear carbonate-based solvent and the cyclic carbonate-based solvent may be mixed in a volume ratio of 9:1 to 1:9. .

The non-aqueous organic solvent according to an embodiment of the present invention may include ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC).

The non-aqueous organic solvent according to an embodiment of the present invention is 10 to 40 wt% of the ethylene carbonate (EC), 5 to 20 wt% of the propylene carbonate (PC), 20 to 60 wt% of the ethylmethyl carbonate (EMC), and 10 to 60 wt% of the diethyl carbonate (DEC).

In addition, the lithium secondary battery according to an embodiment of the present invention,

anode; cathode; separator; and a non-aqueous electrolyte,

The positive electrode includes at least one positive electrode active material selected from the group consisting of lithium composite metal oxide and lithium olivine-type phosphate,

The negative electrode comprises at least one negative electrode active material selected from the group consisting of silicon, a silicon compound, tin, a tin compound, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite, natural graphite, and a mixture of artificial graphite and natural graphite, and ,

The separator includes a porous polymer film alone or a laminate made of at least one polyolefin-based polymer selected from an ethylene polymer, a propylene polymer, an ethylene/butene copolymer, and an ethylene/hexene copolymer, or a ceramic or polymer material is coated including a coated film,

The non-aqueous electrolyte may include a thiocarbonyl compound represented by the following Chemical Formula 1;

electrolyte additive;

lithium salt; and

Non-aqueous organic solvent; includes a lithium secondary battery electrolyte containing.

[Formula 1]

(In Formula 1, R1 and R2 are the same or different from each other, and R1 is each independently hydrogen, deuterium, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or a substituted or unsubstituted ring by combining with an adjacent group to form a ring, and , R2 is each independently hydrogen, deuterium, C1-C6 alkyl group, C3-C6 cycloalkyl group)

And, the positive active material of the lithium secondary battery according to an embodiment of the present invention may include at least one selected from the group consisting of cobalt, manganese, nickel and iron.

The lithium secondary battery using the electrolyte solution for a lithium secondary battery of the present invention has excellent high-temperature life characteristics, and is excellent in reducing internal resistance (IR), suppressing battery thickness expansion, and maintaining capacity during high-temperature storage.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention by these examples.

As used herein, an expression such as "comprising" is understood as an open-ended term that includes the possibility of including other embodiments, unless specifically stated otherwise in the phrase or sentence in which the expression is included. should be

As used herein, “preferred” and “preferably” refer to embodiments of the invention that may provide certain advantages under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Additionally, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

Hereinafter, the electrolyte for a lithium secondary battery of the present invention will be described in detail.

the present invention

a thiocarbonyl compound represented by the following formula (1);

electrolyte additive;

lithium salt; and

It provides an electrolyte solution for a lithium secondary battery comprising; a non-aqueous organic solvent.

[Formula 1]

(In Formula 1, R1 and R2 are the same or different from each other, and R1 is each independently hydrogen, deuterium, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or a substituted or unsubstituted ring by combining with an adjacent group to form a ring, and , R2 is each independently hydrogen, deuterium, C1-C6 alkyl group, C3-C6 cycloalkyl group)

In addition, the thiocarbonyl compound may be O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate (Propargyl-1H-imidazole-1-thiocarboxylate) represented by Formula 2 below.

[Formula 2]

The method for preparing a thiocarbonyl compound represented by Formula 1 includes a first step of reacting a compound represented by Formula 3 and a compound represented by Formula 4 in an organic solvent for synthesis.

[Formula 3]

(In Formula 3, R ₁ is each independently hydrogen, deuterium, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or a substituted or unsubstituted ring bonded to an adjacent group)

[Formula 4]

(In Formula 4, R ₂ is each independently hydrogen, deuterium, a C1-C6 alkyl group, or a C3-C6 cycloalkyl group)

Here, the compound represented by Chemical Formula 3 may be 1,1'-thiocarbonyldiimidazole.

In addition, the compound represented by Formula 4 may be propargyl alcohol (Propargyl alcohol or 2-Propyn-1-ol).

In addition, the first step in which Chemical Formulas 3 and 4 are reacted in an organic solvent for synthesis may be represented by Scheme 1 below.

[Scheme 1]

In addition, 1,1'-thiocarbonyldiimidazole (1,1'-Thiocarbonyldiimidazole) and propargyl alcohol (Propargyl alcohol or 2-Propyn-1-ol) forming the formula (2) are reacted in an organic solvent for synthesis The first step may be represented by Scheme 2 below.

[Scheme 2]

As an embodiment, with respect to 1 equivalent of the compound represented by Formula 4 in the first step, the compound represented by Formula 3 is 1 to 4 equivalents, preferably 1 to 3 equivalents, more preferably 1 to 2 equivalents equivalents can be reacted.

As an embodiment, the reaction temperature of the first step may be -5 to 100 ℃, preferably -5 to 80 ℃, more preferably -5 to 50 ℃. Alternatively, the reaction temperature of the first step may be 10 to 100 ℃, preferably 10 to 80 ℃, more preferably 10 to 50 ℃.

The organic solvent for synthesis is not particularly limited as long as the first-step reaction can proceed, but as a preferred embodiment for the first-step reaction to proceed efficiently, methylene chloride, dichloroethane, and dichloroethane are used as the organic solvent for the synthesis. At least one selected from the group consisting of ethyl ether, diisopropyl ether and tetrahydrofuran may be used.

As an embodiment, the water concentration of the organic solvent for synthesis is 10-1000 ppm, preferably 10-700 ppm, more preferably 10-500 ppm, more preferably 10-300 ppm, more preferably 10 to 200 ppm, more preferably 10 to 100 ppm. When the water concentration of the organic solvent for synthesis is greater than 1000 ppm, the compound represented by Formula 3 may be decomposed by water to generate impurities.

As a more preferred embodiment, the reaction of the first step may proceed under a nitrogen atmosphere.

As an embodiment, in the reaction of the first step, 1,1'-thiocarbonyldiimidazole is added to a flask, methylene chloride is added as an organic solvent for synthesis, and then stirred. , A solution of propargyl alcohol diluted with methylene chloride is added dropwise to proceed with the reaction.

In addition, the method for preparing the thiocarbonyl compound includes a second step of removing the imidazole compound produced in the first step.

In one embodiment, the second step may be removed by washing the imidazole compound with water.

As an embodiment, in the second step, water is added dropwise to the reaction solution of the first step, and when the water dropping is completed, the aqueous layer and the methylene chloride layer are separated. The methylene chloride layer was washed with the same amount of water, and then moisture in the methylene chloride layer washed with magnesium sulfate was removed.

In addition, the method for preparing the thiocarbonyl compound includes a third step of concentrating and recrystallizing the compound dissolved in the organic solvent in the second step.

As an embodiment, the concentration in the third step may be vacuum concentration, and ether may be added to the concentration residue and crystallized in an ice bath to prepare crystals.

And, the thiocarbonyl compound preparation method may further include a fourth step of filtering the concentrated and recrystallized compound and a fifth step of drying the filtrate under vacuum after the third step.

Here, the thiocarbonyl compound may be included in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte for a lithium secondary battery.

In addition, the thiocarbonyl compound may be preferably included in an amount of 0.1 to 10% by weight based on the total weight of the electrolyte for a lithium secondary battery.

When the thiocarbonyl compound is included in an amount of less than 0.05% by weight based on the total weight of the electrolyte for a lithium secondary battery, the effect of preventing battery swelling and reducing the internal resistance of the secondary battery is not sufficient, and the thiocarbonyl compound is the lithium secondary battery If it is contained in an amount exceeding 20% by weight based on the total weight of the electrolyte for a battery, there is a problem in that the battery characteristics such as high-temperature life and high-temperature storage are deteriorated due to an increase in internal resistance and a decrease in capacity of the secondary battery.

And, the electrolyte additive is lithium difluorophosphate (Lithium difluorophosphate), lithium tetrafluoro (oxaleto) phosphate (Lithium tetrafluoro (oxalate) phosphate, lithium bis (fluorosulfonyl) imide (Lithium bis (fluorosulfonyl) imide) ), 1,3-propane sultone, 1,3-propene sultone, fluoroethylene carbonate, vinylene carbonate, And it may include at least one selected from the group consisting of vinyl ethylene carbonate (Vinyl Ethylene Carbonate).

The electrolyte additive may be included in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte for a lithium secondary battery.

When the electrolyte additive is included in an amount of less than 0.05% by weight based on the total weight of the electrolyte for a lithium secondary battery, the thiocarbonyl compound is included in an amount of less than 0.05% by weight based on the total weight of the electrolyte for a lithium secondary battery. When the anti-blowing effect and the internal resistance reduction effect are not sufficient, and the thiocarbonyl compound is included in an amount exceeding 20% by weight based on the total weight of the electrolyte for a lithium secondary battery, a high temperature life due to an increase in internal resistance and a decrease in capacity of the secondary battery; There is a problem in that battery characteristics such as high-temperature storage are deteriorated.

In addition, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , and LiB(C ₂ O ₄ ) ₂ At least one selected from the group consisting of may be included. .

Here, it is preferable to use a lithium salt having a high degree of dissociation of lattice energy, excellent ionic conductivity, and excellent thermal stability and oxidation resistance. The lithium salt serves as a source of lithium ions in the secondary battery to enable basic operation of the lithium battery.

The concentration of the lithium salt may be included in the range of 0.1 to 2.0 M (mol/L) with respect to the total amount of the electrolyte for a lithium secondary battery.

Here, the concentration of the lithium salt may be preferably included in the range of 0.3 to 2.0 M (mol/L) with respect to the total amount of the electrolyte for a lithium secondary battery.

In addition, the concentration of the lithium salt is more preferably 0.7 to 1.6 M (mol/L) in consideration of the properties related to electrical conductivity and the viscosity related to the mobility of lithium ions.

When the concentration of the lithium salt is less than 0.1 M, the electrical conductivity of the electrolyte for a lithium secondary battery is lowered, so that the performance of the non-aqueous electrolyte for transferring ions between the positive and negative electrodes of the lithium secondary battery at a high speed is lowered, and the concentration of the lithium salt is 2.0 M If it exceeds, the viscosity of the electrolyte solution for a lithium secondary battery increases, so that the mobility of lithium ions is reduced and the performance of the secondary battery is deteriorated at a low temperature.

In addition, the non-aqueous organic solvent may be a linear carbonate-based solvent, a cyclic carbonate-based solvent, or a mixture thereof.

The linear carbonate-based solvent is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC) and methyl propyl carbonate (MPC) from the group consisting of It may include at least one or more selected.

In addition, the cyclic carbonate-based solvent is ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3 - It may include at least one selected from the group consisting of pentylene carbonate, vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

Here, among the organic solvent of the linear carbonate-based solvent and the cyclic carbonate-based solvent, a cyclic carbonate-based organic solvent having high ionic conductivity capable of increasing the charge/discharge performance of a secondary battery and a carbonate-based organic solvent having a high dielectric constant It is preferable to use a mixture of a linear carbonate-based organic solvent having a low viscosity that can appropriately control the viscosity of

Specifically, a carbonate-based organic solvent having a high dielectric constant selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), and mixtures thereof as the cyclic carbonate-based solvent, and dimethyl carbonate (DMC) as the linear carbonate-based solvent , diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and a low-viscosity carbonate-based organic solvent selected from the group consisting of mixtures thereof may be mixed and used.

The cyclic carbonate solvent has a large polarity so that it can sufficiently dissociate lithium ions, but has a disadvantage of a large viscosity and low ionic conductivity. It is possible to optimize the characteristics of the battery.

Accordingly, it is preferable to use a mixture of one or more solvents selected from the cyclic carbonate solvent and one or more solvents selected from the linear carbonate solvent as the non-aqueous organic solvent.

Here, the mixed solvent of the linear carbonate-based solvent and the cyclic carbonate-based solvent may be used by mixing the linear carbonate-based solvent and the cyclic carbonate-based solvent in a volume ratio of 9:1 to 1:9.

In addition, the mixed solvent of the linear carbonate-based solvent and the cyclic carbonate-based solvent is used by mixing the linear carbonate-based solvent and the cyclic carbonate-based solvent in a volume ratio of 2:8 to 8:2. It is most preferable in terms of storage characteristics.

In addition, the non-aqueous organic solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC).

In addition, the non-aqueous organic solvent is 10 to 40 wt% of the ethylene carbonate (EC), 5 to 20 wt% of the propylene carbonate (PC), 20 to 60 wt% of the ethylmethyl carbonate (EMC), and the diethyl carbonate (DEC) 10 to 60% by weight.

Specifically, among the cyclic carbonate-based solvents, ethylene carbonate or propylene carbonate having a high dielectric constant is used. When artificial graphite is used as an anode active material, it is preferable to use the ethylene carbonate, and in the linear carbonate-based solvent, viscosity It is preferable to use low dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate.

The lithium secondary battery including the electrolyte has excellent high-temperature life characteristics, and is excellent in reducing internal resistance (IR), suppressing battery thickness expansion, and maintaining capacity during high-temperature storage.

Hereinafter, the lithium secondary battery of the present invention will be described in detail.

The lithium secondary battery of the present invention,

anode; cathode; separator; and a non-aqueous electrolyte,

The positive electrode includes at least one positive electrode active material selected from the group consisting of lithium composite metal oxide and lithium olivine-type phosphate,

The negative electrode comprises at least one negative electrode active material selected from the group consisting of silicon, a silicon compound, tin, a tin compound, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite, natural graphite, and a mixture of artificial graphite and natural graphite, and ,

The separator includes a porous polymer film alone or a laminate made of at least one polyolefin-based polymer selected from an ethylene polymer, a propylene polymer, an ethylene/butene copolymer, and an ethylene/hexene copolymer, or a ceramic or polymer material is coated including a coated film,

The non-aqueous electrolyte may include a thiocarbonyl compound represented by the following Chemical Formula 1;

electrolyte additive;

lithium salt; and

Non-aqueous organic solvent; includes a lithium secondary battery electrolyte containing.

[Formula 1]

(In Formula 1, R1 and R2 are the same or different from each other, and R1 is each independently hydrogen, deuterium, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or a substituted or unsubstituted ring by combining with an adjacent group to form a ring, and , R2 is each independently hydrogen, deuterium, C1-C6 alkyl group, C3-C6 cycloalkyl group)

In addition, the positive active material of the lithium secondary battery may include at least one selected from the group consisting of cobalt, manganese, nickel, and iron.

That is, the lithium secondary battery includes: a) a positive electrode including a positive electrode active material capable of inserting and deintercalating lithium; b) an anode comprising an anode active material capable of intercalating and deintercalating lithium; c) a separator; and d) the electrolyte solution for the lithium secondary battery.

Here, the positive electrode includes at least one positive electrode active material selected from the group consisting of lithium composite metal oxide and lithium olivine-type phosphate.

The negative electrode includes at least one negative electrode active material selected from the group consisting of silicon, a silicon compound, tin, a tin compound, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite, natural graphite, and a mixture of artificial graphite and natural graphite. .

The separator includes a porous polymer film alone or a laminate made of at least one polyolefin-based polymer selected from an ethylene polymer, a propylene polymer, an ethylene/butene copolymer, and an ethylene/hexene copolymer, or a ceramic or polymer material is coated including a coated film.

The non-aqueous electrolyte may include a thiocarbonyl compound represented by the following Chemical Formula 1;

electrolyte additive;

lithium salt; and

Non-aqueous organic solvent; includes a lithium secondary battery electrolyte containing.

[Formula 1]

(In Formula 1, R1 and R2 are the same or different from each other, and R1 is each independently hydrogen, deuterium, a C1-C6 alkyl group, a C3-C6 cycloalkyl group, or a substituted or unsubstituted ring by combining with an adjacent group to form a ring, and , R2 is each independently hydrogen, deuterium, C1-C6 alkyl group, C3-C6 cycloalkyl group)

In addition, non-limiting examples of the lithium 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 cathode active material is preferably a composite metal oxide with lithium and at least one selected from cobalt, manganese, and nickel. The solid solution ratio between cobalt, manganese, and nickel metals of the composite metal oxide may be varied, and in addition to these cobalt, manganese, and nickel metals, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge , Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and an element selected from the group consisting of rare earth elements may be further included.

Specifically, as the positive active material, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , or LiNi _1-xy Co _x M _y O ₂ (0≤x≤1, 0≤y≤1, 0≤x+y ≤ 1, M may use a lithium intercalation compound such as a lithium metal oxide or lithium chalcogenide compound such as Al, Sr, Mg, Mn or La), but is not limited thereto, and can be used as a positive electrode active material in a secondary battery Any material may be used.

The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector. The cathode active material layer may include a cathode active material capable of occluding and releasing lithium, a binder, a conductive material, and the like.

The negative electrode includes a current collector and an anode active material layer formed on the current collector. The anode active material layer may include an anode active material capable of intercalating and deintercalating lithium, a binder, a conductive material, and the like. As the negative electrode active material, crystalline carbon, amorphous carbon, carbon composite material, carbon fiber, lithium metal, lithium alloy, or carbon-metal composite may be used, but is not limited thereto, and any material usable as an anode active material in a secondary battery may be used. have.

The positive electrode and/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 then 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 serving 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, and any binder that can be used by those skilled in the art is possible. For example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene oxide, polyvinyl pyrrolidone, polyurethane, Polytetrafluoroethylene, live vinylidene fluoride (PVdF), polyhexafluoropropylene-polyvinylidene fluoride copolymer (PVdF/HFP)), poly (vinyl acetate), alkylated polyethylene oxide, polyvinyl Ether, poly(methyl methacrylate), poly(ethyl acrylate), polyacrylonitrile, polyvinylpyridine, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber , epoxy resin, nylon, etc. may be used, but is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electrically conductive material that does not cause chemical change may be used. As the conductive material, at least one selected from the group consisting of a graphite-based conductive material, a carbon black-based conductive material, and a metal or metal compound-based conductive material may be used. Examples of the graphite-based conductive material include artificial graphite, natural graphite, and the like, and examples of the carbon black-based conductive material include acetylene black, ketjen black, denka black, thermal black, and channel black ( channel black), and the like, 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 , LaSrMnO ₃ . there is material However, it is not limited to the above-listed conductive materials.

The thickener is not particularly limited as long as it can play a role in controlling the viscosity of the active material slurry, and 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, and the like are dispersed. Examples of the non-aqueous solvent include N-methyl-2-pyrroldidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, or tetrahydrofuran.

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

In addition, the lithium secondary battery may be formed in various shapes, such as a square shape, a cylindrical shape, a pouch type, or a coin type.

Hereinafter, the present invention will be described in more detail through examples. It should not be construed that the scope of the present invention is limited by these examples.

<Synthesis example> Synthesis of O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate (Propargyl-1H-imidazole-1-thiocarboxylate)

A magnetic bar and a thermometer were installed in a 250 mL flask, and 13 g of 1,1'-thiocarbonyldiimidazole (1,1'-Thiocarbonyldiimidazole) was added thereto. As an organic solvent for synthesis, 64 g of methylene chloride with a moisture content of 100 ppm or less is added, stirred, and a solution obtained by diluting 4 g of propargyl alcohol (or 2-Propyn-1-ol) with 40 g of methylene chloride is slowly added dropwise at room temperature. did. After the propargyl alcohol dilution solution was added dropwise and the synthesis reaction was carried out for 1 hour, 64 mL of water was slowly added dropwise to the reaction solution at room temperature, and the by-product imidazole salt was removed by washing with water. When the water drop was completed, the aqueous layer and the methylene chloride layer in the reaction solution were separated, the methylene chloride layer was washed once more with the same amount of water, the moisture in the methylene chloride layer was removed with magnesium sulfate, and the mixture was concentrated in vacuo. 10 g of isopropyl ether was added to the concentrated residue, and crystals of O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate of Formula 2 were prepared in an ice bath at 0 to 5°C. The O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate crystal was filtered, and then the O-(prop-2-yn-1-yl)-1H-imidazole- 1-carbothioate crystals were vacuum dried to obtain 4.75 g of O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate, and the yield was about 40%. (1H 8.39 ppm, 1H 7.76 ppm, 1H 7.06 ppm, 2H 5.42 ppm, 1H 3.32 ppm)

<Example 1>

Preparation of electrolyte solution for lithium secondary battery containing thiocarbonyl compound

After dissolving LiPF ₆ 1.0 M in a mixed solvent of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) (EC/EMC=3/7 volume ratio), 1.0 wt% of fluoroethylene carbonate (FEC) in the mixed solution, 1.0% by weight of lithium difluorophosphate (LiPO ₂ F ₂ ) and O-(prop-2-yn-1-yl) 1H-imidazole-1-carbothioate of the synthesis example represented by Formula 2 above, a thiocarbonyl compound By adding 0.5 wt%, an electrolyte solution for a lithium secondary battery containing a thiocarbonyl compound was prepared.

Preparation of lithium secondary battery containing electrolyte containing thiocarbonyl compound

96 wt% of an NCM-based cathode active material containing Li[Ni _x Co _1-xy Mn _y ]O ₂ (0<x<0.5, 0<y<0.5), 2 wt% of carbon black as a conductive agent, and polyvinylidene as a binder A cathode active material slurry was prepared by adding 2 wt% of fluoride (PVdF) to N-methyl 2-pyrrolidinone (NMP) as an organic solvent. The positive electrode active material slurry was applied to an aluminum thin film as a current collector and dried to prepare a positive electrode, and then rolled by a roll press to prepare a positive electrode.

In addition, graphite as an anode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive agent in 96 wt%, 3 wt%, and 1 wt%, respectively, were added to the organic solvent NMP to prepare an anode active material slurry. The negative electrode active material slurry was applied to a copper thin film serving as a negative electrode current collector and dried to prepare a negative electrode.

In addition, the positive electrode and the negative electrode prepared as described above were prepared, and a separator was interposed therebetween. Then, the electrolyte solution for a lithium secondary battery containing the thiocarbonyl compound is injected between the two electrodes on which the separator is placed, and lithium containing the electrolyte solution containing the thiocarbonyl compound which is an aluminum pouch type (Al-Pouch type) is produced. A secondary battery was manufactured.

<Example 2>

Thiocarbonyl compound and 1,3-propensultone Manufacture of electrolyte for lithium secondary battery

Except for adding 0.5 wt% of 1,3-propene sultone in the manufacturing process of the electrolyte for a lithium secondary battery of Example 1 as an electrolyte, the same as in the preparation of the electrolyte for a lithium secondary battery of Example 1 An electrolyte solution for a lithium secondary battery containing a thiocarbonyl compound and 1,3-propenesultone was prepared by this method.

Preparation of lithium secondary battery containing electrolyte containing thiocarbonyl compound and 1,3-propensultone

A thiocarbonyl compound and 1,3-propensultone were prepared in the same manner as in the preparation of the lithium secondary battery of Example 1, except that the electrolyte solution for a lithium secondary battery containing 1,3-propensultone was used as the electrolyte solution. A lithium secondary battery including the included electrolyte was prepared.

<Comparative Example 1>

Does not contain thiocarbonyl compounds Manufacture of electrolyte for lithium secondary battery

Except for not adding the thiocarbonyl compound O-(prop-2-yn-1-yl)-1H-imidazole-1-carbothioate of the above synthesis example in the manufacturing process of the electrolyte solution for a lithium secondary battery of Example 1 as the electrolyte solution , An electrolyte for a lithium secondary battery that does not contain a thiocarbonyl compound was prepared in the same manner as in the preparation of the electrolyte for a lithium secondary battery of Example 1.

Preparation of a lithium secondary battery containing an electrolyte that does not contain a thiocarbonyl compound

Except for using the electrolyte for a lithium secondary battery that does not add the thiocarbonyl compound that is O-(prop-2-yn-1-yl) 1H-imidazole-1-carbothioate of the synthesis example represented by Formula 2 as the electrolyte solution prepared a lithium secondary battery including an electrolyte solution not containing a thiocarbonyl compound in the same manner as in the preparation of the lithium secondary battery of Example 1.

<Comparative Example 2>

1,3-propensultone and 1,3-propanesultone Manufacture of electrolyte for lithium secondary battery

Without adding the thiocarbonyl compound that is O-(prop-2-yn-1-yl) 1H-imidazole-1-carbothioate of the above synthesis example in the manufacturing process of the electrolyte for a lithium secondary battery of Example 1 as an electrolyte, 1,3- Except for adding 0.5 wt% of propene sultone (1,3-propene sultone) and 0.5 wt% of 1,3-propane sultone (1,3-propane sultone), the electrolyte solution for a lithium secondary battery of Example 1 An electrolyte solution for a lithium secondary battery containing 1,3-propensultone and 1,3-propanesultone was prepared in the same manner as described above.

Preparation of lithium secondary battery containing electrolyte containing 1,3-propensultone and 1,3-propanesultone

Without adding the thiocarbonyl compound that is O-(prop-2-yn-1-yl) 1H-imidazole-1-carbothioate of the above synthesis example represented by Formula 2 as the electrolyte solution, the 1,3-propensultone and 1,3-propensultone and 1,3-propanesultone were included in the same manner as in the preparation of the lithium secondary battery of Example 1, except that the electrolyte solution for a lithium secondary battery containing 1,3-propanesultone was used. A lithium secondary battery containing an electrolyte solution was prepared.

Table 1 below shows the composition of the electrolyte solution for lithium secondary batteries of Examples and Comparative Examples.

Composition of electrolyte for lithium secondary battery Thiocarbonyl Compounds
(Synthesis example) 1,3-propene
sulton 1,3-propane
sulton Fluorethylene carbonate
(FEC) lithium difluorophosphate
(LiPO ₂ F ₂ ) Example 1 О О О Example 2 О О О О Comparative Example 1 О О Comparative Example 2 О О О О

<Experimental example>

<Experimental Example 1> Evaluation of high temperature life characteristics

After charging the pouch-shaped lithium secondary battery prepared using the electrolyte for lithium secondary batteries of the above Examples and Comparative Examples at 1C-rate to 4.2 V at high temperature (45 ℃), with a rest time of 10 minutes, 2.7 V at 1C-rate After discharging to , there was a rest time of 10 minutes again. The above process was repeated 400 times to measure the battery's discharge capacity (mAh) and lifetime efficiency (efficiency, %), and Table 2 below shows the measured discharge capacity and lifetime efficiency.

Lithium secondary battery discharge capacity and efficiency 1 time
Discharge capacity (mAh) 400 discharge capacity (mAh) Life Efficiency (%) Example 1 929.6 827.7 89.0 Example 2 942.9 846.5 89.8 Comparative Example 1 933.2 824.8 88.4 Comparative Example 2 943.0 801.2 85.0

As shown in Table 2, as a result of the life evaluation at high temperature, it was confirmed that the lithium secondary battery of Example 1 had better life efficiency at high temperature than the lithium secondary battery of Comparative Example 1. In addition, it was confirmed that the lithium secondary battery of Example 2 had better lifetime efficiency at high temperature than the lithium secondary battery of Comparative Example 2.

Accordingly, the lithium secondary batteries of Examples 1 and 2 include the electrolyte solution containing the thiocarbonyl compound represented by Chemical Formula 2, and thus have a higher temperature than the lithium secondary batteries of Comparative Examples 1 and 2 It was confirmed that the life efficiency of the lithium secondary battery was better.

<Experimental Example 2> Evaluation of IR, battery thickness and capacity retention rate after leaving at high temperature

The lithium secondary battery in the form of a pouch prepared using the electrolyte solution for lithium secondary batteries of the above Examples and Comparative Examples was left at a high temperature (60 ° C) for 10 weeks, and then IR (internal resistance), battery thickness and capacity retention were measured. The measured results are shown.

IR (%) Battery thickness (%) Capacity retention rate (%) Example 1 103 8.0 84 Example 2 70 2.0 85 Comparative Example 1 138 17 68 Comparative Example 2 81 2.0 85

As shown in Table 3, it was confirmed that Example 1 was superior to Comparative Example 1 in the IR, battery thickness, and capacity retention ratio results after leaving at high temperature.

Comparing Example 1 and Comparative Example 1, the synthesis represented by Formula 2 in fluorethylene carbonate (FEC) and lithium difluorophosphate (LiPO ₂ F ₂ ) contained in the electrolyte of the lithium secondary battery of Comparative Example 1 The lithium secondary battery of Example 1 containing the electrolyte solution of Example 1 including the thiocarbonyl compound that is O-(prop-2-yn-1-yl) 1H-imidazole-1-carbothioate of Example 1 had high-temperature lifespan performance. It was confirmed that the IR, battery thickness, and capacity retention rate characteristics of high temperature storage performance were all excellent.

In addition, as shown in Table 3, in the IR, battery thickness and capacity retention ratio results after leaving at high temperature, Example 2 showed excellent performance in which the IR was further reduced without change in the battery thickness and capacity retention ratio compared to Comparative Example 2. there was.

Comparing Example 2 and Comparative Example 2, fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO ₂ F ₂ ), 1,3-propanesultone (1) contained in the electrolyte of the lithium secondary battery of Comparative Example 2 ,3-propane sultone) and 1,3-propene sultone, instead of 1,3-propane sultone, O-( The lithium secondary battery of Example 2 containing the electrolyte of Example 2 containing the thiocarbonyl compound of prop-2-yn-1-yl) 1H-imidazole-1-carbothioate had the battery thickness and capacity of high-temperature storage performance. It was confirmed that the performance was improved due to the reduction of IR and the high temperature life performance was excellent without deterioration of the retention rate characteristics.

That is, the lithium secondary batteries of Examples 1 and 2 include the electrolyte solution containing the thiocarbonyl compound represented by Chemical Formula 2, and thus have a higher temperature than the lithium secondary batteries of Comparative Examples 1 and 2 It was confirmed that the lifetime performance was excellent, and the IR, battery thickness and capacity retention characteristics of high temperature storage performance were all excellent.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (15)

A thiocarbonyl compound which is O-(prop-2-yn-1-yl) 1H-imidazole-1-carbothioate (Propargyl-1H-imidazole-1-thiocarboxylate) represented by the following formula (2);
electrolyte additive;
lithium salt; and
Non-aqueous organic solvent; Lithium secondary battery electrolyte containing.
[Formula 2]

delete The method of claim 1,
The thiocarbonyl compound is characterized in that it is included in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte for a lithium secondary battery.
Electrolyte for lithium secondary batteries.
The method of claim 1,
The electrolyte additive is lithium difluorophosphate (Lithium difluorophosphate), lithium tetrafluoro (oxaleto) phosphate (Lithium tetrafluoro (oxalate) phosphate, lithium bis (fluorosulfonyl) imide (Lithium bis (fluorosulfonyl) imide), 1,3-propane sultone, 1,3-propene sultone, fluoroethylene carbonate, vinylene carbonate, and vinyl Ethylene carbonate (Vinyl Ethylene Carbonate) characterized in that it comprises at least one selected from the group consisting of
Electrolyte for lithium secondary batteries.
The method of claim 1,
The electrolyte additive is characterized in that it is included in an amount of 0.05 to 20% by weight based on the total weight of the electrolyte for a lithium secondary battery.
Electrolyte for lithium secondary batteries.
The method of claim 1,
The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , and LiB(C ₂ O ₄ ) ₂ Characterized in that it contains at least one selected from the group consisting of
Electrolyte for lithium secondary batteries.
The method of claim 1,
The concentration of the lithium salt is characterized in that it is contained in 0.1 to 2.0 M (mol / L) with respect to the total amount of the lithium secondary battery electrolyte.
Electrolyte for lithium secondary batteries.
The method of claim 1,
The non-aqueous organic solvent is a linear carbonate-based solvent, a cyclic carbonate-based solvent, or a mixture thereof.
Electrolyte for lithium secondary batteries.
9. The method of claim 8,
The linear carbonate-based solvent is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC) and methyl propyl carbonate (MPC) from the group consisting of Characterized in that it comprises at least one or more selected
Electrolyte for lithium secondary batteries.
9. The method of claim 8,
The cyclic carbonate-based solvent is ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pen Characterized in that it contains at least one selected from the group consisting of tylene carbonate, vinylene carbonate (VC) and fluoroethylene carbonate (FEC).
Electrolyte for lithium secondary batteries.
9. The method of claim 8,
The mixed solvent of the linear carbonate-based solvent and the cyclic carbonate-based solvent is characterized in that the linear carbonate-based solvent and the cyclic carbonate-based solvent are mixed in a volume ratio of 9:1 to 1:9
Electrolyte for lithium secondary batteries.
9. The method of claim 8,
The non-aqueous organic solvent is characterized in that it comprises ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC).
Electrolyte for lithium secondary batteries.
13. The method of claim 12,
The non-aqueous organic solvent is 10 to 40 wt% of the ethylene carbonate (EC), 5 to 20 wt% of the propylene carbonate (PC), 20 to 60 wt% of the ethylmethyl carbonate (EMC), and the diethyl carbonate (DEC) ) characterized in that it comprises 10 to 60% by weight
Electrolyte for lithium secondary batteries.
anode; cathode; separator; and a non-aqueous electrolyte,
The positive electrode includes at least one positive electrode active material selected from the group consisting of lithium composite metal oxide and lithium olivine-type phosphate,
The negative electrode comprises at least one negative electrode active material selected from the group consisting of silicon, a silicon compound, tin, a tin compound, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite, natural graphite, and a mixture of artificial graphite and natural graphite, and ,
The separator includes a porous polymer film alone or a laminate made of at least one polyolefin-based polymer selected from an ethylene polymer, a propylene polymer, an ethylene/butene copolymer, and an ethylene/hexene copolymer, or a ceramic or polymer material is coated including a coated film,
The non-aqueous electrolyte comprises the lithium secondary battery electrolyte of any one of claims 1 and 13, and
lithium secondary battery.
15. The method of claim 14,
The positive active material is characterized in that it comprises at least one selected from the group consisting of cobalt, manganese, nickel and iron.
lithium secondary battery.