阅读说明：本技术 化合物及包含该化合物的锂二次电池电解质和锂二次电池 (Compound, lithium secondary battery electrolyte comprising same, and lithium secondary battery ) 是由 郑景文 李相镇 李晟澈 于 2019-11-29 设计创作，主要内容包括：本发明提供一种由式1表示的化合物、一种包含所述化合物的用于锂二次电池的电解质和一种包括所述电解质的锂二次电池。(The present invention provides a compound represented by formula 1, an electrolyte for a lithium secondary battery comprising the same, and a lithium secondary battery comprising the electrolyte.)

1. A compound represented by the following formula 1:

[ formula 1]

In the formula 1, the first and second groups,

x1 and X2 are each independently-O-, -S-, or-NR' -,

r' is a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain heteroatoms or halogen atoms,

x3 and X4 are each independently carbon, phosphorus or sulfur,

however, at least one of X3 and X4 is phosphorus or sulfur,

a is boron or phosphorus, and the content of A is,

each R is independently: hydrogen; a halogen atom; a linear, branched or cyclic C1 to C10 hydrocarbon group that may contain a halogen atom; OR'; or OSiR'₃；

L is: a C1 hydrocarbon group unsubstituted or substituted with a halogen atom; or oxygen;

m is lithium, sodium, potassium or ammonium (NR "₄)，

Each R "is independently: hydrogen; or a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain a heteroatom or a halogen atom,

a and a' are each independently an integer of 0 to 2,

b and b' are each independently an integer of 0 to 2,

c is an integer of 0 to 4,

d is an integer of 0 to 3,

e is an integer of 1 to 3, and

however, b-a and b '-a' are integers of 0 or more.

2. The method of claim 1, wherein the compound represented by formula 1 is further defined as follows:

in formula 1, when X3 or X4 is carbon, a is 0 or 1, a 'is 0 or 1, b is 1 or 2, and b' is 1 or 2,

when X3 or X4 is phosphorus, a is 0 or 1, a 'is 0 or 1, b is 1 or 2, and b' is 1 or 2,

when X3 or X4 is sulfur, a is an integer of 0 to 2, a 'is an integer of 0 to 2, b is an integer of 0 to 2, and b' is an integer of 0 to 2,

when A is boron, c is 0 or 2,

c is 0, 2 or 4 when A is phosphorus;

when L is carbon, d is an integer of 0 to 3, and

when L is oxygen, d is 0 or 1.

3. The compound according to claim 2, wherein the compound represented by formula 1 is represented by any one of the following formulae 2 to 13:

[ formula 2]

[ formula 3]

[ formula 4]

[ formula 5]

[ formula 6]

[ formula 7]

[ formula 8]

[ formula 9]

[ formula 10]

[ formula 11]

[ formula 12]

[ formula 13]

4. An electrolyte for a lithium secondary battery comprising the compound according to any one of claims 1 to 3.

5. The electrolyte for a lithium secondary battery according to claim 4, wherein the compound is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the entire electrolyte for a lithium secondary battery.

6. The electrolyte for a lithium secondary battery according to claim 5, wherein the compound is contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the entire electrolyte for a lithium secondary battery.

7. The electrolyte for a lithium secondary battery according to claim 4, further comprising at least one selected from the group consisting of a lithium salt and an organic solvent.

8. A lithium secondary battery comprising the electrolyte for a lithium secondary battery according to claim 4.

Technical Field

The present application claims the benefit of priority from korean patent application No. 10-2019-0036233, filed on 28/3/2019, and korean patent application No. 10-2019-0110984, filed on 6/9/2019, which are incorporated herein by reference in their entirety.

The present invention relates to a novel compound, an electrolyte for a lithium secondary battery comprising the same, and a lithium secondary battery comprising the electrolyte.

Background

With the realization of miniaturization and weight reduction of electronic equipment and the widespread use of portable electronic devices, research into secondary batteries having high energy density as their power sources has been actively conducted.

Examples of the secondary battery may include a nickel-cadmium battery, a nickel metal hydride battery, a nickel hydrogen battery, and a lithium secondary battery. Among them, research into lithium secondary batteries having high energy density per unit weight and capable of rapid charging has been increasing.

In general, a lithium ion secondary battery is manufactured by using materials capable of intercalating and deintercalating lithium ions as a positive electrode and a negative electrode, and filling a space between the positive electrode and the negative electrode with a nonaqueous electrolyte. Since an oxidation reaction and a reduction reaction occur when lithium ions are intercalated into and deintercalated from the cathode and the anode, electric energy is generated.

Meanwhile, in order to increase the capacity of the lithium secondary battery, the internal resistance should be low. However, the larger the internal resistance, the greater the advantage in terms of the safety of the battery. The capacity and safety of a lithium secondary battery are closely related to the characteristics of a nonaqueous electrolyte, which is composed of a solute (such as an electrolyte salt) and a nonaqueous organic solvent.

Korean patent laid-open publication No. 2018-0036340 relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same, and discloses contents regarding an electrolyte for a lithium secondary battery, the electrolyte including: a non-aqueous organic solvent, a lithium salt, and an additive comprising the compound represented by formula 1.

Korean patent laid-open publication No. 2013-0003649 relates to an electrolyte solution additive for a lithium secondary battery, and a nonaqueous electrolyte solution and a lithium secondary battery comprising the same, and discloses contents regarding a nonaqueous electrolyte solution additive for a lithium secondary battery, the additive including a bidentate alkoxyphosphine compound represented by formula 1.

However, it is difficult to process conventional compounds for lithium secondary battery electrolytes because low-molecular substances are vaporized during synthesis, resulting in a decrease in yield and an increase in cost. In addition to these problems, there are problems that oxidation stability is deteriorated, so that the reliability of the battery is lowered and the output of the battery is reduced.

Meanwhile, korean patent laid-open publication No. 2018-0038038 relates to a nonaqueous electrolyte solution and a nonaqueous electrolyte battery using the same, and specifically discloses contents regarding a nonaqueous electrolyte solution comprising a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent, the nonaqueous electrolyte solution comprising: (I) a difluoro ion complex (1-Cis) represented by the general formula (1-Cis); and (II) at least one compound selected from the group consisting of: cyclic sulfonic acid esters, cyclic sulfonic acid esters having an unsaturated bond, cyclic sulfuric acid esters, cyclic disulfonic acid esters, chain disulfonic acid esters, cyclic disulfonic acid anhydrides, nitrile group-containing compounds, silyl phosphate derivatives, and silyl borate derivatives.

However, in the case of the prior art document, the solubility of the lithium salt is limited, and the Lowest Unoccupied Molecular Orbital (LUMO) level is somewhat low, resulting in a problem of side reactions accompanied by decomposition of the lithium salt at the negative electrode. In addition, since the electrolyte solution uses an organic ligand, some occurs in which CO is generated₂The problem of gas.

Therefore, it is required to develop an electrolyte for a lithium secondary battery that allows the battery to exhibit high output characteristics.

Documents of the prior art

Patent document

(patent document 1) korean patent laid-open publication No. 2018-0036340 (published by 4 and 9 in 2018)

(patent document 2) Korean patent laid-open publication No. 2013-0003649 (published in 2013, 1 month and 9 days)

(patent document 3) Korean patent laid-open publication No. 2018-0038038 (published in 2018, 4 and 13)

Disclosure of Invention

Problems to be solved by the invention

The object of the present invention is to provide: a novel compound which, when applied to an electrolyte for a lithium secondary battery, allows the battery to exhibit high output characteristics and to exhibit sufficient performance even after storage at high temperatures, while suppressing an increase in the thickness of the battery by suppressing the generation of volatile substances; and an electrolyte for a lithium secondary battery comprising the compound.

Further, another object of the present invention is to provide a lithium secondary battery including the electrolyte, which has high output characteristics, exhibits a large charge and discharge capacity even at room temperature at a high C-rate and may exhibit sufficient performance even after storage at high temperature.

Means for solving the problems

To achieve the above object, according to one aspect of the present invention, there is provided a compound represented by the following formula 1:

[ formula 1]

In the formula 1, the first and second groups,

x1 and X2 are each independently-O-, -S-, or-NR' -,

r' is a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain heteroatoms or halogen atoms,

x3 and X4 are each independently carbon, phosphorus or sulfur,

however, at least one of X3 and X4 is phosphorus or sulfur,

a is boron or phosphorus, and the content of A is,

each R is independently: hydrogen; a halogen atom; a linear, branched or cyclic C1 to C10 hydrocarbon group that may contain a halogen atom; OR'; or OSiR'₃；

L is: a C1 hydrocarbon group unsubstituted or substituted with a halogen atom; or oxygen;

m is lithium, sodium, potassium or ammonium (NR "₄)，

Each R "is independently: hydrogen; or a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain a heteroatom or a halogen atom,

a and a' are each independently an integer of 0 to 2,

b and b' are each independently an integer of 0 to 2,

c is an integer of 0 to 4,

d is an integer of 0 to 3,

e is an integer of 1 to 3, and

however, b-a and b '-a' are integers of 0 or more.

Further, the present invention provides an electrolyte for a lithium secondary battery, comprising the compound described above.

In addition, the present invention provides a lithium secondary battery including the electrolyte for a lithium secondary battery described above.

Advantageous effects

According to the present invention, there are the following advantages. The compound according to the present invention has excellent solubility, and can impart excellent reliability when applied to an electrolyte for a lithium secondary battery.

Further, the electrolyte for a lithium secondary battery according to the present invention allows the battery to exhibit high output characteristics and exhibit sufficient performance even after storage at high temperatures, while making it possible to suppress an increase in the thickness of the battery by suppressing the generation of volatile substances.

In addition, the lithium secondary battery including the electrolyte for a lithium secondary battery according to the present invention has high output characteristics and exhibits a large charge and discharge capacity even at room temperature at a high C-rate, while possibly exhibiting sufficient performance even after storage at high temperature and suppressing an increase in the thickness of the battery.

Detailed Description

Hereinafter, the present invention will be described in more detail.

In the present invention, when the explanatory phrase that a member is located "on" another member is used, this includes not only the case where the member is in direct contact with the another member but also the case where the another member is interposed between two members.

In the present invention, when an explanatory phrase that a part "includes" a component is used, this means that the part may further include the component but does not exclude other components, as long as it is not particularly explained.

Compound (I)

One aspect of the present invention relates to a compound represented by the following formula 1:

[ formula 1]

In the formula 1, the first and second groups,

x1 and X2 are each independently-O-, -S-, or-NR' -,

r' is a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain heteroatoms or halogen atoms,

x3 and X4 are each independently carbon, phosphorus or sulfur,

however, at least one of X3 and X4 is phosphorus or sulfur,

a is boron or phosphorus, and the content of A is,

each R is independently: hydrogen; a halogen atom; a linear, branched or cyclic C1 to C10 hydrocarbon group that may contain a halogen atom; OR'; or OSiR'₃；

L is: a C1 hydrocarbon group unsubstituted or substituted with a halogen atom; or oxygen;

m is lithium, sodium, potassium or ammonium (NR "₄)，

Each R "is independently: hydrogen; or a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain a heteroatom or a halogen atom,

a and a' are each independently an integer of 0 to 2,

b and b' are each independently an integer of 0 to 2,

c is an integer of 0 to 4,

d is an integer of 0 to 3,

e is an integer of 1 to 3, and

however, b-a and b '-a' are integers of 0 or more.

As used herein, "heteroatom" refers to O, N or S as a heterogeneous element.

As used herein, "halogen atom" refers to F, Cl, Br, or I.

As used herein, "hydrocarbyl group" may refer to straight or branched chain aliphatic hydrocarbon groups and cyclic aliphatic hydrocarbon groups.

The straight or branched aliphatic hydrocarbon group may include: straight-chain aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl and the like; branched aliphatic hydrocarbon groups such as isopropyl group, isobutyl group, isopentyl group, neopentyl group, and 2-ethylhexyl group, etc. The number of carbon atoms of the aliphatic hydrocarbon group is 1 to 6, preferably 1 to 5, and more preferably 1 to 4.

The cyclic (cyclo) aliphatic hydrocarbon group may be monocyclic or polycyclic. The cyclic aliphatic hydrocarbon group may include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like. The number of carbon atoms of the cyclic aliphatic hydrocarbon group is 3 to 8, and preferably 3 to 6.

The compounds according to the invention have the advantage of excellent solubility.

When the inorganic ligand-containing lithium salt compound having high polarity represented by formula 1 according to the present invention is used as an additive for an electrolyte of a lithium secondary battery, there are advantages in that the compound can be easily adsorbed to the surface of an electrode through an oxidation reaction to form a stable film, thereby imparting low resistance and high output, and reducing problems caused by volatilization of organic materials. Because of this, there is an advantage in that a battery including the compound can exhibit excellent life characteristics and high-temperature stability at room temperature.

In one embodiment of the present invention, the compound represented by formula 1 may be further defined as follows:

in formula 1, when X3 or X4 is carbon, a may be 0 or 1, a 'may be 0 or 1, b may be 1 or 2, and b' may be 1 or 2,

when X3 or X4 is phosphorus, a can be 0 or 1, a 'can be 0 or 1, b can be 1 or 2, and b' can be 1 or 2,

when X3 or X4 is sulfur, a may be an integer of 0 to 2, a 'may be an integer of 0 to 2, b may be an integer of 0 to 2, and b' may be an integer of 0 to 2,

when A is boron, c may be 0 or 2,

when A is phosphorus, c can be 0, 2 or 4;

when L is carbon, d can be an integer from 0 to 3, and

when L is oxygen, d may be 0 or 1.

For example, the compound represented by formula 1 may be represented by X3 or X4 and a combination of a and L.

In another embodiment of the present invention, the compound represented by formula 1 may be represented by any one of formulae 2 to 13 below.

[ formula 2]

[ formula 3]

[ formula 4]

[ formula 5]

[ formula 6]

[ formula 7]

[ formula 8]

[ formula 9]

[ formula 10]

[ formula 11]

[ formula 12]

[ formula 13]

When the compound according to the present invention is any one of the compounds represented by formulae 2 to 13, it may have more excellent solubility, and thus is preferable.

In particular, when any one of the compounds represented by formulae 2 to 13 is used as an electrolyte for a lithium secondary battery, there is an advantage in that generation of volatile gas is suppressed while improving the battery output.

The compound represented by formula 1 may be synthesized, for example, in the following manner: mixing LiPF₆Or LiBF₄Dissolved in carbonate solutionTo the reagent, the ligand is then slowly added, the trimethylsilyl group is introduced thereto in as much as the necessary equivalent, followed by 12 to 24 hours of reaction by increasing the temperature to 40 to 80 ℃.

Since the compound according to the present invention is an inorganic ligand, when it is applied as an electrolyte for a lithium secondary battery, there is an advantage in that it is possible to maximize the output of the battery while suppressing CO during the oxidation of the existing organic ligand₂And (4) gas generation.

Electrolyte for lithium secondary battery

Another aspect of the present invention relates to an electrolyte for a lithium secondary battery, comprising the compound described above.

Specifically, another aspect of the present invention relates to an electrolyte for a lithium secondary battery, which includes a compound represented by formula 1 below:

[ formula 1]

In the formula 1, the first and second groups,

x1 and X2 are each independently-O-, -S-, or-NR' -,

r' is a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain heteroatoms or halogen atoms,

x3 and X4 are each independently carbon, phosphorus or sulfur,

however, at least one of X3 and X4 is phosphorus or sulfur,

a is boron or phosphorus, and the content of A is,

each R is independently: hydrogen; a halogen atom; a linear, branched or cyclic C1 to C10 hydrocarbon group that may contain a halogen atom; OR'; or OSiR'₃；

L is: a C1 hydrocarbon group unsubstituted or substituted with a halogen atom; or oxygen;

m is lithium, sodium, potassium or ammonium (NR "₄)，

Each R "is independently: hydrogen; or a linear, branched or cyclic C1 to C10 hydrocarbon group which may contain a heteroatom or a halogen atom,

a and a' are each independently an integer of 0 to 2,

b and b' are each independently an integer of 0 to 2,

c is an integer of 0 to 4,

d is an integer of 0 to 3,

e is an integer of 1 to 3, and

however, b-a and b '-a' are integers of 0 or more.

Since the electrolyte for a lithium secondary battery according to the present invention includes the above-described compound, there are advantages in that the compound can be easily adsorbed to the surface of an electrode through an oxidation reaction to form a stable film, thereby imparting low resistance and high output, and reducing problems caused by volatilization of organic materials.

In another embodiment of the present invention, the compound may be included in an amount of 0.01 to 10 parts by weight, based on 100 parts by weight of the entire electrolyte for a lithium secondary battery.

In another embodiment of the present invention, the compound may be included in an amount of 0.1 to 5.0 parts by weight, and specifically 0.2 to 5 parts by weight, based on 100 parts by weight of the entire electrolyte for a lithium secondary battery.

When the compound is contained within the above range, the effects of low resistance and high output are maximized, and thus it is preferable.

In another embodiment of the present invention, the electrolyte for a lithium secondary battery may further comprise at least one selected from the group consisting of a lithium salt and an organic solvent.

The lithium salt serves as a source of lithium ions in the battery to achieve basic operation of the lithium battery. The concentration of the lithium salt may be 0.5 to 1.5M, but is not limited thereto. However, when the concentration of the lithium salt is within the above range, the electrical conductivity of the electrolyte may be decreased to suppress a phenomenon of deterioration of electrolyte performance, and the viscosity of the electrolyte may be increased to suppress a phenomenon of decrease in mobility of lithium ions. In short, when the concentration of the lithium salt is within the above range, there are advantages in that the electrolyte has excellent electrical conductivity and excellent properties, while the viscosity of the electrolyte is suitable for ensuring excellent mobility of lithium ions. However, the concentration of the lithium salt is not limited to the above range, and it is possible to use by appropriately adding or subtracting the concentration.

For example, the lithium salt may use one selected from the group consisting of: LiPF₆、LiBF₄、LiSbF₆、LiAsF₆、LiClO₄、LiCF₃SO₃、LiN(SO₂F)₂、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiC(SO₂CF₃)₃、LiN(SO₃CF₃)₂、LiC₄F₉SO₃、LiAlO₄、LiAlCl₄LiCl and LiI or a mixture of two or more thereof, but not limited thereto. However, in this case, the fluidity of lithium ions is very excellent, and the electrical conductivity is excellent, so that the electrolyte has excellent properties.

The organic solvent may include at least one solvent selected from the group consisting of a high dielectric constant solvent and a low boiling point solvent.

Specifically, the high dielectric constant solvent is not particularly limited as long as it is commonly used in the art, and for example, cyclic carbonates such as fluorinated ethylene carbonate, propylene carbonate, butylene carbonate, 1-fluorinated ethylene carbonate, γ -butyrolactone, and/or mixtures thereof, and the like may be used.

The low boiling point solvent may use, for example, a chain carbonate (such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, etc.), dimethoxyethane, diethoxyethane, fatty acid ester derivatives and/or a mixture thereof, but is not limited thereto.

An organic solvent may be included as a balancing agent so as to satisfy 100 parts by weight of the entire electrolyte for a lithium secondary battery. In this case, the lithium salt and the compound described above have excellent intended effects and are therefore preferable.

The electrolyte for a lithium secondary battery according to the present invention may further include other additives. Specifically, the electrolyte for a lithium secondary battery according to the present invention may further include an additive other than the compound represented by formula 1.

In short, the compound represented by formula 1 according to the present invention may be used as an additive for forming a film on a positive electrode of an electrolyte for a lithium secondary battery.

The other additive may be, for example, at least one selected from the group consisting of: fluorocarbonic acid esters, vinylene carbonate, oxalyl tetrafluorophosphate lithium salt, bis (oxalyl) difluorophosphate lithium salt, trioxyl phosphate lithium salt, and LiPO₂F₂At least one of (1).

When other additives are further included, there is an advantage in that the effect of the compound represented by formula 1 is further maximized.

The other additives may be contained in an amount of 0.5 to 10 parts by weight, and specifically 1 to 3 parts by weight, based on 100 parts by weight of the entire electrolyte additive for a lithium secondary battery. In this case, reliability such as life characteristics at room temperature and high-temperature stability of the lithium secondary battery are increased, and thus it is preferable.

The electrolyte of the lithium secondary battery according to the present invention may be specifically a non-aqueous electrolyte, and the compound of the present invention may be specifically used as an additive for a non-aqueous electrolyte.

Specifically, the electrolyte for a lithium secondary battery according to the present invention allows the battery to exhibit high output characteristics, have a large charge-discharge capacity even at room temperature at a high rate (high C-rate), and exhibit sufficient performance even after storage at high temperatures, while making it possible to suppress an increase in the thickness of the battery by suppressing the generation of volatile substances.

Lithium secondary battery

Another aspect of the present invention relates to a lithium secondary battery including the electrolyte for a lithium secondary battery described above.

The electrolyte for a lithium secondary battery according to the present invention is manufactured into a lithium ion secondary battery by injecting it into an electrode structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator forming the electrode structure may use all of them as long as they are commonly used in the manufacture of a lithium secondary battery.

The positive electrode and the negative electrode are prepared by applying the positive electrode active material slurry and the negative electrode active material slurry to the respective electrode collectors.

As the positive electrode active material, a positive electrode active material capable of intercalating and deintercalating lithium ions known in the art may be used without particular limitation thereto, and for example, at least one selected from cobalt, manganese, nickel, and one or more lithium composite oxides is preferably used. As representative examples thereof, lithium-containing compounds described below are preferably used.

Li_xMn_1-yM_yA₂ (1)

Li_xMn_1-yM_yO_2-zX_z (2)

Li_xMn₂O_4-zX_z (3)

Li_xMn_2-yM_yM'_zA₄ (4)

Li_xCo_1-yM_yA₂ (5)

Li_xCo_1-yM_yO_2-zX_z (6)

Li_xNi_1-yM_yA₂ (7)

Li_xNi_1-yM_yO_2-zX_z (8)

Li_xNi_1-yCo_yO_2-zX_z (9)

Li_xNi_1-y-zCo_yM_zA_α (10)

Li_xNi_1-y-zCo_yM_zO_2-αX_α (11)

Li_xNi_1-y-zMn_yM_zA_α (12)

Li_xNi_1-y-zMn_yM_zO_2-αX_α (13)

In the formula, X, y, z and α may range from 0.9. ltoreq. x.ltoreq.1.1, 0. ltoreq. y.ltoreq.0.5, 0. ltoreq. z.ltoreq.0.5 and 0. ltoreq. α.ltoreq.2, M and M' are the same or different from each other and may be selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V and rare earth elements, A is selected from the group consisting of O, F, S and P, and X is selected from the group consisting of F, S and P.

As the anode active material, an anode active material capable of intercalating and deintercalating lithium ions known in the art may be used without particular limitation thereto, and as such an anode active material, a carbon-based material (such as crystalline carbon, amorphous carbon, carbon composite, carbon fiber, and the like), metallic lithium, a lithium alloy, and the like may be used. For example, amorphous carbon may include hard carbon, coke, Mesophase Carbon Microbeads (MCMB) calcined at 1500 ℃ or less, mesophase pitch-based carbon fibers (MPCF), and the like. The crystalline carbon may include graphite-based carbon, and specifically natural graphite, graphite coke, graphite MCMB, graphite MPCF, and the like.

The carbon-based material preferably has a d002 interplanar spacing of 3.35 to 3.35And a crystallite size (Lc) measured by X-ray diffraction of 20nm or more. As the lithium alloy, an alloy of lithium and aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium may be used.

The positive electrode active material and the negative electrode active material may be mixed with a binder and a solvent, respectively, to prepare a positive electrode active material slurry and a negative electrode active material slurry.

The binder is a material that exerts functions of forming active materials into a slurry, adhering the active materials to each other, adhering to a current collector, and buffering expansion and contraction of the active materials, and may include, for example, polyvinylidene fluoride, polyhexafluoropropylene-polyvinylidene fluoride copolymer (P (VdF/HFP)), poly (vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly (meth) methacrylate, poly (ethyl acrylate), polytetrafluoroethylene, polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and the like. The content of the binder is 0.1 to 30 parts by weight, and preferably 1 to 10 parts by weight, based on 100 parts by weight of the entire electrode active material. If the content of the binder is too small, the adhesion between the electrode active material and the current collector is insufficient. If the content of the binder is too large, the adhesive force is improved, but the content of the electrode active material is reduced as much as the increased content, thereby being disadvantageous in realizing a battery having a high capacity.

As the solvent of the active material slurry, a nonaqueous solvent or an aqueous solvent can be generally used. As the nonaqueous solvent, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, and the like can be used, and as the aqueous solvent, water, isopropanol, and the like can be used, but not limited thereto.

The electrode active material slurry may further contain a conductive material, a thickener, and the like, as necessary.

The conductive material is a material for improving electron conductivity, and at least one selected from the group consisting of a graphite-based conductive material, a carbon black-based conductive material, and a metal-based or metal compound-based conductive material may be used. Examples of the graphite-based conductive material include artificial graphite, natural graphite, and the like, examples of the carbon black-based conductive material include acetylene black, ketjen black, superconducting acetylene black (denka black), thermal black, channel black, and the like, and examples of the metal-based or metal compound-based conductive material include perperovskite materials such as tin, tin oxide, tin phosphate (SnPO)₄) Titanium oxide, potassium titanate, LaSrCoO₃And LaSrMnO₃And the like. But are not limited to, the conductive materials listed above.

The content of the conductive material is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the entire electrode active material. If the content of the conductive material is less than 0.1 parts by weight, electrochemical characteristics may be deteriorated, and if it exceeds 10 parts by weight, energy density per unit weight may be decreased.

The thickener is not particularly limited as long as it can exert an effect of controlling the viscosity of the active material slurry, but for example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and the like can be used.

The positive and negative electrode active material slurries prepared as described above were applied to electrode collectors to prepare positive and negative electrodes. In this case, aluminum or an aluminum alloy may be used as the positive electrode collector, and copper or a copper alloy may be used as the negative electrode collector. Types of the positive electrode collector and the negative electrode collector may include foil, film, sheet, stamped part, porous body, foam, and the like.

The prepared positive and negative electrodes were manufactured in an electrode structure with a separator interposed therebetween, and then disposed in a battery case, into which an electrolyte was then injected to manufacture a lithium secondary battery. As separator, the following can be used alone or by laminating: conventional porous polymer films, which are commonly used as separators, for example polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene/butene copolymers, ethylene/hexene copolymers and ethylene/methacrylate copolymers. Alternatively, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of glass fibers having a high melting point, polyethylene terephthalate fibers, or the like, may also be used, but is not limited thereto.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be manufactured in a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

Since the lithium secondary battery according to the present invention includes the electrolyte for a lithium secondary battery including the compound represented by formula 1, there are advantages in that high output characteristics can be exhibited and sufficient performance can be exhibited even after storage at high temperature, while it is possible to suppress an increase in the thickness of the battery by suppressing the generation of volatile substances.

Hereinafter, the embodiments will be described to more specifically understand the present invention. However, it will be apparent to those skilled in the art that various modifications and variations can be made to such embodiments as defined in the appended claims, and the scope of the present invention is of course not limited to the following embodiments. Such embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Further, unless the context indicates otherwise, it indicates that the following "%" and "part" are based on weight.

Synthesis example 1

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, and then 2 equivalents of dimethylbis (trimethylsilyl) ultradiphosphate was slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent was removed by a distillation apparatus, and the remaining volatile matter was removed by vacuum drying to synthesize the compound represented by formula 2.

[ formula 2]

The synthesized compound shows¹H NMR DMSO delta 3.8ppm, P-NMR DMSO delta-20.4 ppm, delta-145.7 ppm, F-NMR DMSO delta 71ppm and ICP-MS Li: P ratio 1:4.8 (calculated 1: 5).

Synthesis example 2

1 equivalent of lithium hexafluorophosphate (LiPF)₆) After dissolving in dimethyl carbonate solvent, 2 equivalents of bis (tetramethylsilyl) pyrophosphate were slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent was removed by a distillation apparatus, and the remaining volatile matter was removed by vacuum drying to synthesize the compound represented by formula 3.

[ formula 3]

The synthesized compound shows¹H NMR acetone delta 0.8ppm, P-NMR acetone delta-30.4 ppm, delta-144.3 ppm, F-NMR acetoneδ 72ppm, and ICP-MS Li: P: Si ratio 1:4.7:4.6 (calculated 1:5: 5).

Synthesis example 3

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, and then 2 equivalents of difluoro (trimethylsilyl) pyrophosphate were slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent was removed by a distillation apparatus, and the remaining volatile matter was removed by vacuum drying to synthesize the compound represented by formula 4.

[ formula 4]

The synthesized compound showed P-NMR DMSO delta-35.5 ppm, delta-14.7 ppm, F-NMR DMSO delta-71 ppm and ICP-MS Li: P ratio 1:4.6 (calculated 1: 5).

Synthesis example 4

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, and then 2 equivalents of trimethylsilylethoxytrimethylsilyloxyphosphinate were slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent was removed by a distillation apparatus, and the remaining volatile matter was removed by vacuum drying to synthesize the compound represented by formula 5.

[ formula 5]

The synthesized compound shows¹H NMR DMSO delta 3.1 delta 1.4ppm, P-NMR DMSO delta-30.1 ppm, delta-149.2 ppm, F-NMR DMSO delta-72 ppm and ICP-MS Li: P ratio 1:1.9 (calculated 1: 2).

Synthesis example 5

1 equivalent of lithium tetrafluoroborate (LiBF4) was dissolved in a dimethyl carbonate solvent, and then 2 equivalents of dimethylbis (trimethylsilyl) ultradiphosphate was slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent was removed by a distillation apparatus, and the remaining volatile matter was removed by vacuum drying to synthesize the compound represented by formula 6.

[ formula 6]

The synthesized compound shows¹H NMR DMSO delta 1.8ppm, P-NMR DMSO delta-28.8 ppm, B-NMR DMSO delta 2.8ppm, F-NMR DMSO delta-61 ppm and ICP-MS Li: P: B ratio 1:1.8:0.92 (calculated 1:2: 1).

Synthesis example 6

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, then 2 equivalents of hydroxymethanesulfonic acid were added, followed by a temperature drop to 0 ℃. Then, 3 equivalents of tetrachlorosilane were slowly added dropwise, and the reaction was carried out at 45 ℃ for 24 hours. After the completion of the reaction, the solvent is removed by a distillation apparatus, and the remaining volatile matter is removed by vacuum drying, to synthesize the compound represented by formula 7.

[ formula 7]

The synthesized compound shows¹H NMR DMSO delta 2.2ppm, P-NMR DMSO delta-149.6 ppm, F-NMR DMSO delta-74 ppm and ICP-MS Li: P: S ratio 1:0.98:2.96 (calculation 1:1: 2).

Synthesis example 7

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, then 2 equivalents of dimethyl diphosphonic acid were added, followed by a temperature drop to 0 ℃.3 equivalents of tetrachlorosilane were slowly added dropwise and the reaction was carried out at 45 ℃ for 24 hours. After completion of the reaction, the solvent was removed by a distillation apparatus, and the residual volatile matter was removed by vacuum drying to synthesize a compound represented by formula 8The compounds shown are shown.

[ formula 8]

The synthesized compound shows¹H NMR DMSO delta 2.8ppm, P-NMR DMSO delta-28.2 ppm, delta-148.8 ppm, F-NMR DMSO delta-72 ppm and ICP-MS Li: P ratio 1:4.7 (calculated 1: 5).

Synthesis example 8

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, and then 2 equivalents of bis (trimethylsilyl) methanedisulfonate was slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent is removed by a distillation apparatus, and the remaining volatile matter is removed by vacuum drying, to synthesize the compound represented by formula 9.

[ formula 9]

The synthesized compound shows¹H NMR DMSO delta 5.3ppm, P-NMR DMSO delta-33.4 ppm, delta-150.2 ppm, F-NMR DMSO delta-60 ppm and ICP-MS Li: P: S ratio 1:0.9:3.9 (Calcd. 1:1: 4).

Synthesis example 9

1 equivalent of boron trifluoride (BF3) was dissolved in a dimethyl carbonate solvent, 1 equivalent of lithium methylenedisulfonate was slowly added dropwise, and then a reaction was carried out at 45 ℃ for 24 hours. The solid was recovered by filtration under reduced pressure, washed with 20g of Ethyl Methyl Carbonate (EMC), and further dried under reduced pressure at 40 ℃ for 3 hours. After the completion of the reaction, the solvent is removed by a distillation apparatus, and the remaining volatile substances are removed by vacuum drying, to synthesize the compound represented by formula 10.

[ formula 10]

The synthesized compound shows¹H NMR DMSO delta 0.8ppm, B-NMR DMSO delta 1.6ppm, F-NMR DMSO delta-62 ppm and ICP-MS Li: B: S ratio 1:0.9:1.9 (calculation 1:1: 2).

Synthesis example 10

1 equivalent of lithium hexafluorophosphate (LiPF)₆) Dissolved in dimethyl carbonate solvent, and then 2 equivalents of bis (trimethylsilyl) difluorodiphosphate was slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent is removed by a distillation apparatus, and the remaining volatile substances are removed by vacuum drying, to synthesize the compound represented by formula 11.

[ formula 11]

The synthesized compound showed P-NMR DMSO delta-33.4 ppm, delta-149.2 ppm, F-NMR DMSO delta-72 ppm and ICP-MS Li: P: Si ratio 1:2.8 (calculated 1: 3).

Synthesis example 11

1 equivalent of lithium tetrafluoroborate (LiBF)₄) Dissolved in dimethyl carbonate solvent, and then 2 equivalents of tetrakis (trimethylsilyl) diphosphate was slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent is removed by a distillation apparatus, and the remaining volatile matter is removed by vacuum drying, to synthesize the compound represented by formula 12.

[ formula 12]

The synthesized compound shows¹H NMR DMSO delta 0.8ppm, P-NMR DMSO delta-25.6 ppm, B-NMR DMSO delta 2.7ppm and ICP-MS Li: B: P: Si ratio 1:0.9:3.8:3.6 (calculated 1:1:4: 4).

Synthesis example 12

1 equivalent of lithium tetrafluoroborate (LiBF4) was dissolved in a dimethyl carbonate solvent, and then 2 equivalents of bis (trimethylsilyl) difluorodiphosphate was slowly added dropwise, followed by reaction at 45 ℃ for 24 hours. After the completion of the reaction, the solvent is removed by a distillation apparatus, and the remaining volatile matter is removed by vacuum drying, to synthesize the compound represented by formula 13.

[ formula 13]

The synthesized compound showed P-NMR DMSO delta-33.4 ppm, F-NMR DMSO delta-72 ppm, B-NMR DMSO delta 3.2ppm and ICP-MS Li: B: P ratio 1:0.96:3.8 (calculation 1:1: 4).

Example 1

(1) Preparation of positive and negative electrodes

97.3 parts by weight of LiCoO₂As a positive electrode active material, 1.4 parts by weight of polyvinylidene fluoride as a binder and 1.3 parts by weight of ketjen black as a conductive material were mixed and then dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry. The prepared positive active material slurry was coated on an aluminum foil, dried, and then rolled to prepare a positive electrode.

Further, 98 parts by weight of graphite as a negative electrode active material, 1 part by weight of polyvinylidene fluoride as a binder, and 1 part by weight of ketjen black as a conductive material were mixed and then dispersed in N-methylpyrrolidone to prepare a negative electrode active material layer composition. The prepared negative active material layer composition was applied to a copper foil, dried, and then rolled to prepare a negative electrode.

(2) Preparation of electrolyte for lithium secondary battery

By mixing 0.95M LiPF₆To a mixed solution of Ethylene Carbonate (EC), diethyl carbonate (DEC), and Ethyl Propionate (EP) in a volume ratio of 40:40:20 to prepare a non-aqueous mixed solution.

To this was added 3.0 parts by weight of a compound represented by formula 2 below, based on 100 parts by weight of the total non-aqueous mixed solution, to prepare an electrolyte for a lithium secondary battery.

[ formula 2]

(3) Production of lithium secondary battery

A lithium secondary battery was manufactured using the positive and negative electrodes prepared according to (1) above and the electrolyte prepared according to (2) above.

Examples 2 to 12

A lithium secondary battery was manufactured according to the same procedure as described in example 1, except that compounds represented by formulas 3 to 13 below were added instead of the compound represented by formula 2, respectively.

[ formula 3]

[ formula 4]

[ formula 5]

[ formula 6]

[ formula 7]

[ formula 8]

[ formula 9]

[ formula 10]

[ formula 11]

[ formula 12]

[ formula 13]

Comparative example 1

(1) Preparation of positive and negative electrodes

The positive and negative electrodes were prepared according to the same procedure as described in example 1.

(2) Preparation of electrolyte

By mixing 0.95M LiPF₆To a mixed solution of Ethylene Carbonate (EC), diethyl carbonate (DEC), and Ethyl Propionate (EP) in a volume ratio of 40:40:20 to prepare a non-aqueous mixed solution.

(3) Production of lithium secondary battery

A lithium secondary battery was manufactured using the positive and negative electrodes prepared according to (1) above and the electrolyte prepared according to (2) above.

Comparative example 2

A lithium secondary battery was manufactured according to the same procedure as described in example 1, except that lithium trioxylphosphate was used instead of the compound represented by formula 2.

Comparative example 3

A lithium secondary battery was fabricated according to the same procedure as described in example 1, except that lithium bis (oxalyl) difluorophosphate (LiFOB (LiB (C)) was used₂O₄)₂) Instead of the compound represented by formula 2.

Experimental examples

The secondary batteries prepared according to examples and comparative examples were subjected to constant current charging at a current density of 0.2C at 25 ℃ until the voltage reached 4.2V, and then to constant current discharging at a current density of 0.2C until the voltage reached 2.5V. Then, the secondary battery was subjected to constant current charging at a current density of 0.5C until the voltage reached 4.2V, and then to constant voltage charging while maintaining 4.2V until the current density reached 0.05C. Then, the secondary battery was subjected to constant current discharge at a current density of 0.5C until the voltage at the time of discharge reached 2.5V (formation step).

(1) Life characteristics at room temperature

The secondary battery subjected to the formation step was subjected to constant current charging at a current density of 1.0C at 25 ℃ until the voltage reached 4.2V, and was charged at a constant voltage while maintaining 4.2V until the current density reached 0.05C. Then, a cycle of discharging at a constant current of 1.0C until the voltage reaches 2.5V during the discharge was repeated 300 times.

The capacity retention (%) of each secondary battery at the 300 th cycle was calculated from the following formula 1, and the results thereof are shown in the following table 1.

[ equation 1]

Capacity retention rate [% ] x 100 [ discharge capacity at 300 th cycle/discharge capacity at 1 st cycle ] ×

(2) High temperature stability

The secondary battery subjected to the formation step was subjected to constant current charging at a current density of 1.0C at 25 ℃ until the voltage reached 4.2V, and was charged at a constant voltage while maintaining 4.2V until the current density reached 0.05C. Then, when the charged secondary battery was stored at 60 ℃, voltage was measured every 24 hours using a multimeter to measure the remaining voltage of the state-of-charge battery at high temperature to determine high-temperature voltage storage stability.

The voltage retention (%) of each secondary battery measured on day 15 was calculated from the following formula 2, and the results thereof are shown in table 1 below.

[ equation 2]

Voltage retention [% ] x 100 [ open circuit voltage at day 15/initial open circuit voltage ] ×

(3) Rate of increase of thickness

The lithium secondary batteries prepared according to examples and comparative examples were subjected to constant current charging at a current density of 1C until a voltage of 4.45V was reached. After charging, the thickness was measured, and the rate of change in thickness (%) was measured when stored at 60 ℃ for 28 days. The thickness change rate of each secondary battery at the time of measurement on day 28 was calculated by the following formula 3, and the results thereof are shown in table 1 below.

[ equation 3]

Thickness increase rate [% ] x 100 [ thickness of secondary battery/initial thickness of secondary battery on day 28 ] ×

(4) Rate of increase of internal resistance

The internal resistances of the lithium secondary batteries prepared according to the examples and comparative examples were measured. The internal resistance measurement was performed by adjusting to 50% of the battery capacity (SOC-50%), then flowing currents of 0.5A, 1A, 2A, 3A, and 5A, and the battery voltage after 10 seconds was measured. The measured current and voltage are approximated to be straight lines, and the internal resistance is obtained from the slope. The resistance increase rate, which represents the rate at which the internal resistance increases when charging and discharging are repeated in the same manner as described above, was evaluated.

By setting the internal resistance of the 1 st cycle as the initial internal resistance R1(Ω) and the internal resistance of the 300 th cycle as the internal resistance R300(Ω) after the cycle in the charge/discharge cycle test, the resistance increase rate was calculated using the following formula 4, and the results thereof are shown in table 1 below.

[ equation 4]

Rate of increase of resistance R_ma(％)＝(R300-R1)/R1×100

[ Table 1]

Referring to table 1, it can be seen that in the examples in which the electrolyte for a lithium secondary battery comprising the compound according to the present invention was injected as an additive, both the thickness increase rate and the resistance increase rate were small, while having excellent life characteristics at room temperature and high-temperature stability.