KR101195931B1 - Non-aqueous electrolyte solution for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a nonaqueous electrolyte for a lithium secondary battery and a lithium secondary battery having the same. According to the present invention, a nonaqueous electrolyte solution for a lithium secondary battery including an ionizable lithium salt and an organic solvent includes: (a) 1 part by weight to 10 parts by weight of a compound containing a vinylene group or a vinyl group, based on 100 parts by weight of the total nonaqueous electrolyte; And (b) 10 parts by weight to 300 parts by weight of the multinitrile compound having an ether bond of a specific structure based on 100 parts by weight of the vinylene group or the compound containing a vinyl group. The lithium secondary battery provided with the nonaqueous electrolyte of the present invention can effectively suppress the swelling phenomenon of the battery and improve the charge / discharge cycle life.

Description

Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery having same {NON-AQUEOUS ELECTROLYTE SOLUTION FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a non-aqueous electrolyte lithium secondary battery having a multi-nitrile-based additive improves cycle life and excellent effect of suppressing the swelling phenomenon and a lithium secondary battery having the same.

Recently, interest in energy storage technology is increasing. As the field of application extends to the energy of mobile phones, camcorders, notebook PCs, and even electric vehicles, the demand for high energy density of batteries used as power sources for such electronic devices is increasing. Lithium secondary batteries are the ones that can best meet these demands, and researches on them are actively under way.

Among the secondary batteries currently applied, lithium secondary batteries developed in the early 1990's include lithium salts dissolved in an appropriate amount of a negative electrode such as a carbon material capable of occluding and releasing lithium ions, a positive electrode made of lithium-containing oxide, and a mixed organic solvent. It consists of a nonaqueous electrolyte.

Recently, as the use of lithium secondary batteries expands, demand for lithium secondary batteries that can maintain excellent performance even in harsher environments such as high or low temperature environments and can be safely charged even at high voltage is increasing.

By the way, the lithium transition metal oxide or composite oxide used as a positive electrode active material of a lithium secondary battery has a structural safety and capacity determined by occlusion and release of lithium ions, and their capacity increases as the charging potential increases, but accordingly Release of transition metals and the like may also be accelerated, resulting in structural instability.

In addition, organic solvents currently widely used in nonaqueous electrolytes include ethylene carbonate, propylene carbonate, dimethoxyethane, gamma butyrolactone, N, N-dimethylformamide, tetrahydrofuran or acetonitrile. However, such organic solvents generally show deterioration of the battery due to gas generation and swelling due to oxidation of the electrolyte when stored for a long time at high temperature. The decomposition gas generated at this time deforms the pouch-type or can-type battery assembly, causing an internal short circuit, and in severe cases, the battery may ignite or explode. However, the oxidation of the electrolyte may be further accelerated by the transition metal eluted under high voltage conditions.

In order to solve this problem, various additives have been proposed to prevent the swelling of the battery in the non-aqueous electrolyte, but has not yet effectively solved the problem. For example, when succinonitrile is added to the electrolyte, the swelling phenomenon of the battery can be somewhat suppressed, but there is a problem that the charge and discharge cycle life is lowered.

Accordingly, an object of the present invention is to provide a lithium secondary battery nonaqueous electrolyte and a lithium secondary battery having the same, which can suppress the swelling phenomenon of a battery and at the same time improve the charge / discharge cycle life.

In order to solve the said subject, the nonaqueous electrolyte solution for lithium secondary batteries containing the ionizable lithium salt and organic solvent in accordance with this invention is a compound containing a vinylene group or a vinyl group as an additive with respect to 100 weight part of said all nonaqueous electrolyte solutions. 1 part by weight to 10 parts by weight; And (b) 10 parts by weight to 300 parts by weight of a multinitrile compound having an ether bond represented by the following Formula 1 based on 100 parts by weight of the vinylene group or a compound containing a vinyl group:

In Formula 1,

R ¹ , R ² , R ³ and R ⁴ are each independently alkylene or alkenylene having 1 to 5 carbon atoms,

At least one of R ⁵ and R ⁶ is a nitrile bonded to a heteroalkyl group having 1 to 10 carbon atoms containing oxygen or sulfur, and the remainder is halogen or alkyl, alkenyl, alkylamine or aryl having 1 to 10 carbon atoms.

In the present invention, "vinylene group" is defined as -CH = CH-, and "vinyl group" is defined as CH ₂ = CH-. As the compound containing a vinylene group or a vinyl group according to the present invention, a vinylene carbonate compound, an acrylate compound containing a vinyl group, a sulfonate compound containing a vinyl group, an ethylene carbonate compound containing a vinyl group, and the like are each alone. Or two or more kinds thereof can be mixed. Representative examples of the vinylene carbonate-based compound include vinylene carbonate. More specifically, the compound containing the vinyl group may be represented by the following formula (2):

In Chemical Formula 2,

At least one of R ₁ to R ₄ includes a vinyl group, and the remaining ones are each independently hydrogen, halogen, halogen or unsubstituted C ₁ to C ₆ alkyl group, C ₆ to C ₁₂ aryl group, C ₂ to An alkenyl group or a sulfonate group of C ₆ .

In the nonaqueous electrolyte solution of the present invention, the multinitrile compound having an ether bond is 1,2,3-tris (2-cyanoethoxy) propane, 1,1,1-tris (cyanoethoxymethyl) ethane, 1,3-bis (2-cyanoethoxy) -2,2-bis (2-cyanoethoxymethyl) propane, and 3,3-[[2-[(2-cyanoethoxy) methyl] -2-ethyl-1,3propanediyl] bis (oxy)] bis [propanenitrile] and the like may be used alone or in combination of two or more thereof, but is not limited thereto.

Optionally, the nonaqueous electrolyte of the present invention may further include a cyclic carbonate substituted with halogen represented by the following Formula 3.

In Chemical Formula 1,

X and Y are each independently hydrogen, chlorine, or fluorine, and X and Y are not simultaneously hydrogen.

In the cyclic carbonate substituted with halogen according to the present invention, the mixed content with the vinylene group or the compound containing the vinyl group may be used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the nonaqueous electrolyte.

In the non-aqueous liquid electrolyte of the present invention, the lithium salt anion is the anion is ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, AlO 4 -, _{^{AlCl 4 -, PF 6 -,}} SbF 6 -, AsF 6 -, BF 2 C 2 O 4 -, BC 4 O 8 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF ^{_{3) 4 PF 2 -, (}} CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, C 4 F 9 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2 _{^{) 2 N -, (FSO 2}} ) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 _{^{C -, CF 3 (CF 2}} ) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- may be any one of ^{_{-, (CF 3 CF 2 SO}} 2) 2 N.

In the nonaqueous electrolyte of the present invention, the organic solvent may be used alone or in combination of two or more of ether, ester, linear carbonate, and cyclic carbonate.

The nonaqueous electrolyte of the present invention can be used as an electrolyte of a lithium secondary battery in the form of a gel polymer electrolyte impregnated with a liquid electrolyte or a polymer per se.

The nonaqueous electrolyte solution of this invention can provide the lithium secondary battery which can suppress the swelling phenomenon of a battery and can also improve the charge / discharge cycle life. In particular, it is excellent in suppressing swelling phenomenon and improving charge and discharge cycle life under high temperature and high voltage conditions.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical spirit of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.
1 is a graph showing the change in thickness of a battery over time as a result of measuring the swelling phenomenon at high temperature and high voltage conditions for the battery of Example 1 and Comparative Example 1 of the present invention.
FIG. 2 is a graph showing a maintenance capacity fraction relative to an initial capacity according to the number of charge and discharge cycles under high temperature conditions of the batteries of Example 1 and Comparative Example 1. FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

According to the present invention, a nonaqueous electrolyte solution for a lithium secondary battery including an ionizable lithium salt and an organic solvent includes: (a) 1 part by weight to 10 parts by weight of a compound containing a vinylene group or a vinyl group, based on 100 parts by weight of the total nonaqueous electrolyte; And (b) 10 parts by weight to 300 parts by weight of the multinitrile compound having an ether bond represented by the following Formula 1 based on 100 parts by weight of the vinylene group or the compound containing a vinyl group.

[Formula 1]

In Formula 1,

R ¹ , R ² , R ³ and R ⁴ are each independently alkylene or alkenylene having 1 to 5 carbon atoms,

At least one of R ⁵ and R ⁶ is a nitrile bonded to a heteroalkyl group having 1 to 10 carbon atoms containing oxygen or sulfur, and the remainder is halogen or alkyl, alkenyl, alkylamine or aryl having 1 to 10 carbon atoms.

In the present invention, "vinylene group" is defined as -CH = CH-, and "vinyl group" is defined as CH ₂ = CH-. Examples of the vinylene group or the compound containing a vinyl group include a vinylene carbonate compound, an acrylate compound containing a vinyl group, a sulfonate compound containing a vinyl group, an ethylene carbonate compound containing a vinyl group, or the like. It can mix and use species.

More specifically, the vinylene carbonate-based compound may be vinylene carbonate, and the compound containing the vinyl group may include a compound represented by the following Chemical Formula 2.

[Formula 2]

In Formula 2,

Of _{R 1, R 2, R 3} , R 4 , at least one of which contains a vinyl group, and the remains are each independently substituted with hydrogen, halogen, halogen or unsubstituted C alkyl group of _{1 ~ C 6, C 6 ~} C 12 an aryl group, an alkenyl group, or sulfonate group of C ₂ ~ C _6.

In the non-aqueous electrolyte of the present invention, the vinylene group or the compound containing a vinyl group is 1 part by weight to 10 parts by weight, preferably 1 part by weight to 7 parts by weight, and more preferably 1 part by weight based on 100 parts by weight of the total non-aqueous electrolyte. To 5 parts by weight. If the content is less than 1 part by weight, the effect of improving swelling in a high temperature environment is insignificant, and if it exceeds 10 parts by weight, high rate charge / discharge characteristics are deteriorated due to an increase in electrode interface resistance.

When used in the nonaqueous electrolyte of the battery, the vinylene group or the compound containing the vinyl group used in the present invention forms a passivation film called SEI membrane on the surface of the negative electrode during initial charging to suppress the reduction decomposition of carbonate used as the nonaqueous solvent, The discharge efficiency is improved to exhibit good cycle characteristics.

However, when the vinylene group or the compound containing the vinyl group according to the present invention is used in the carbonate electrolyte, there is a disadvantage in that the decomposition gas is easily vulnerable at high temperature because the decomposition gas is deformed in the pouch type or can type battery assembly. May cause a short circuit and, if severe, may cause the battery to ignite or explode.

As described above, gas generation during the high temperature storage described above tends to increase as the amount of the additive forming the film in the cathode increases. In particular, in the case of vinylene carbonate (VC) after forming the SEI film in the cathode at the beginning of use, the VC remaining on the electrolyte is oxidized on the anode during high temperature storage to act as a cause of rapid gas generation. In particular, when a lithium transition metal oxide is used as the positive electrode active material, the transition metal serves as an oxidizing agent to promote decomposition of the electrolyte, and further accelerates the oxidative decomposition reaction at high temperature.

However, since the multinitrile compound having an ether bond according to the present invention has three or more nitrile groups, it is possible to easily form a complex on the surface of the positive electrode composed of lithium-transition metal oxide, thereby oxidizing the electrolyte and the positive electrode. It is possible to suppress the heat generation by suppressing, and to prevent the internal short circuit caused by the rapid temperature rise of the battery. In addition, when the high temperature storage, the decomposition of the above-described vinylene group or a compound containing a vinyl group and the electrolyte solution is suppressed to have an effect of suppressing the battery swelling phenomenon.

In addition, various compounds are present in the nonaqueous electrolyte during charge and discharge, among which HF and PF ₅ make the nonaqueous electrolyte an acidic atmosphere. By the way, the oxidation reaction at the anode surface of the nonaqueous electrolyte solution mentioned above is accelerated in an acidic atmosphere.

However, oxygen (-O-) in the multinitrile compound having an ether bond according to the present invention can be combined with HF, PF ₅ and the like in the nonaqueous electrolyte to suppress the acidic atmosphere composition and also suppress the oxidative decomposition reaction of the nonaqueous electrolyte.

Furthermore, the multinitrile compound having an ether bond according to the present invention may exhibit an improved effect than conventional additives in terms of performance of the battery, and in particular, the capacity retention rate is excellent, and thus the electrochemical characteristics such as improvement of charge and discharge cycle lifespan are excellent. A battery can be provided.

Specific examples of the multinitrile compound having an ether bond represented by Formula 1 include 1,2,3-tris (2-cyanoethoxy) propane, 1,1,1-tris (cyanoethoxymethyl) ethane , 1,3-bis (2-cyanoethoxy) -2,2-bis (2-cyanoethoxymethyl) propane and 3,3-[[2-[(2-cyanoethoxy) methyl] -2-ethyl-1,3propanediyl] bis (oxy)] bis [propanenitrile] may be any one selected from the group consisting of, or a mixture of two or more thereof.

The multinitrile compound having an ether bond according to the present invention is preferably included in 10 parts by weight to 300 parts by weight based on 100 parts by weight of the vinylene group or a compound containing a vinyl group. If the content is less than 10 parts by weight, the effect of preventing swelling is insignificant, and if it exceeds 300 parts by weight, the ionic conductivity of the non-aqueous electrolyte is lowered, resulting in a high rate of charge and discharge characteristics. In this respect, the multinitrile compound having an ether bond according to the present invention is more preferably from 30 parts by weight to 300 parts by weight, most preferably from 50 parts by weight to 100 parts by weight of a vinylene group or a compound containing a vinyl group. 250 parts by weight may be included in the nonaqueous electrolyte.

Optionally, in the nonaqueous electrolyte of the present invention, a cyclic carbonate substituted with halogen may be further included. The cyclic carbonate substituted with halogen may be used together with the vinylene group or the compound containing the vinyl group to improve the physical properties of the SEI film formed on the surface of the negative electrode, thereby further enhancing the battery bulging prevention effect.

The cyclic carbonate substituted with halogen according to the present invention may be represented by the following Chemical Formula 3:

(3)

In Chemical Formula 1,

X and Y are each independently hydrogen, chlorine, or fluorine, and X and Y are not simultaneously hydrogen.

The cyclic carbonate substituted with the halogen is preferably 1 to 10 parts by weight with respect to the vinylene group or a compound containing a vinyl group with respect to 100 parts by weight of the nonaqueous electrolyte. In addition, the mixing ratio of a vinylene group or a compound containing a vinyl group with a cyclic carbonate substituted with halogen may be appropriately selected depending on the specific use in which the battery is used. For example, a cyclic carbonate: vinylene group or vinyl group substituted with halogen Contains compound = 1: 0.5 to 5 may have a weight ratio, but is not limited thereto. When the weight ratio of the vinylene group or the compound containing the vinyl group to the cyclic carbonate substituted with halogen is less than 0.5, the high temperature charge / discharge performance is weakened, and if it is more than 5, the interfacial resistance of the negative electrode is greatly increased and the initial performance of the battery is reduced. This may be because the vinylene group or the compound containing the vinyl group forms a relatively dense SEI film, but should not be construed as being limited thereto.

In addition, the present invention further provides a compound capable of forming a passivation film on the surface of the negative electrode in addition to the above-described vinylene group or a compound containing a vinyl group and a cyclic carbonate substituted with halogen, without departing from the scope of the present invention. It may include. Non-limiting examples of such compounds include sulfur-containing compounds such as propane sultone, ethylene sulfite, propene sultone, and lactam compounds such as N-acetyl lactam.

The lithium salt contained as an electrolyte in a non-aqueous liquid electrolyte of the present invention can be used without limitation, those which are commonly used in a lithium secondary battery electrolyte, such as the lithium salt, the anion is F ^-, Cl ^-, Br ^-, I ^{-, _{NO 3 -, N (CN)}} 2 -, BF 4 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 -, AsF 6 -, BF 2 C 2 O 4 -, BC 4 O _{^{8 -, (CF 3) 2}} PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 _{^{-, C 4 F 9 SO 3}} -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF ^{_{3 SO 2) 2 CH -,}} (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

As the organic solvent included in the non-aqueous electrolyte of the present invention described above, those conventionally used in the lithium secondary battery electrolyte may be used without limitation, and for example, ether, ester, linear carbonate, cyclic carbonate, etc. may be used alone or two kinds. It can mix and use the above.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included. Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, and any one selected from the group consisting of halides thereof or mixtures of two or more thereof. Specific examples of the linear carbonate compounds include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate. Any one selected or a mixture of two or more thereof may be representatively used, but is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, are highly viscous organic solvents, and thus may be preferably used because they dissociate lithium salts in the electrolyte well, such as dimethyl carbonate and diethyl carbonate. When the same low viscosity, low dielectric constant linear carbonate is mixed and used in an appropriate ratio, an electrolyte having high electrical conductivity can be made, and thus it can be used more preferably.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone, ε-caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The nonaqueous electrolyte solution for a lithium secondary battery of the present invention described above is accommodated in a battery container, an electrode assembly composed of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and then injected into a battery container to manufacture a lithium secondary battery. As the positive electrode, the negative electrode, and the separator constituting the electrode assembly, all of those conventionally used in manufacturing a lithium secondary battery may be used.

As a specific example, a lithium-containing transition metal oxide may be preferably used as the cathode active material. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), and Li _x MnO ₂ (0.5 <x <1.3), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ (0.5 <x <1.3, 0 <a <1, 0 < b <1, 0 <c <1, a + b + c = 1), Li _x Ni _{1 -y} Co _y O ₂ (0.5 <x <1.3, 0 <y <1), Li _x Co _{1 -y} Mn _y O ₂ (0.5 <x <1.3, 0 ≦ y <1), Li _x Ni _{1- y} Mn _y O ₂ (0.5 <x <1.3, O ≦ y <1), Li _x (Ni _a Co _b Mn _c ) O ₄ (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 -z} Ni _z O ₄ (0.5 < x <1.3, 0 <z <2), Li _x Mn _{2 -z} Co _z O ₄ (0.5 <x <1.3, 0 <z <2), Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ (0.5 <x <1.3) may be used any one selected from the group consisting of or a mixture of two or more thereof, and the lithium-containing transition metal oxide may be coated with a metal or metal oxide such as aluminum (Al). . In addition to the lithium-containing transition metal oxide, sulfide, selenide, halide, and the like may also be used.

As the negative electrode active material, a carbon material, lithium metal, silicon, tin, or the like, which can normally occlude and release lithium ions, may be used, and a metal oxide such as TiO ₂ and SnO ₂ having a potential of less than ₂ V may be used. Preferably, a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch-based carbon fiber. High temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, Mesophase pitches and petroleum or coal tar pitch derived cokes.

The positive electrode and / or the negative electrode may include a binder, and the binder may include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile ), An organic binder such as polymethylmethacrylate, or an aqueous binder such as styrene-butadiene rubber (SBR) can be used together with a thickener such as carboxymethyl cellulose (CMC). Preferably, it is possible to use an aqueous binder that is excellent in adhesion and exhibits excellent adhesion even when using only a relatively small amount.

In addition, as the separator, conventional porous polymer films conventionally used as separators, for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc. The porous polymer film made of the polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. It is not.

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

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example  One

<Production of Nonaqueous Electrolyte>

A nonaqueous electrolyte of 1M LiPF ₆ solution having a composition of ethylene carbonate: propylene carbonate: diethyl carbonate = 3: 2: 5 (weight ratio) was prepared under Ar atmosphere. 1 part by weight, 3 parts by weight of fluoro ethylene carbonate (FEC), and 1 part by weight of 1,2,3-tris (2-cyanoethoxy) propane (3-CEP) were further added to the nonaqueous electrolyte.

<Manufacture of battery>

A positive electrode slurry was prepared by mixing LiCoO ₂ as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon at a weight ratio of 93: 4: 4 with a conductive material, and then dispersing it in N-methyl-2-pyrrolidone. It was. The slurry was coated on aluminum foil having a thickness of 15 μm, and then dried and rolled to prepare a positive electrode.

In addition, natural graphite as a negative electrode active material, styrene-butadiene rubber as a binder and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 96: 2: 2, and then dispersed in water to prepare a negative electrode slurry. The slurry was coated on 10 μm thick copper foil, followed by drying and rolling to prepare a negative electrode.

Thereafter, the prepared positive electrode and the negative electrode were prepared together with the porous separator by a conventional method in a pouch-type battery, and the electrolyte was injected to complete the battery manufacturing.

Example  2

An electrolyte solution and a battery were prepared in the same manner as in Example 1, except that 1,2,3-tris (2-cyanoethoxy) propane was added in 2 parts by weight.

Example  3

An electrolyte solution and a battery were prepared in the same manner as in Example 1, except that 1,2,3-tris (2-cyanoethoxy) propane was added in 3 parts by weight.

Example  4

An electrolyte solution and a battery were prepared in the same manner as in Example 1, except that 2 parts by weight of vinylene carbonate and 2 parts by weight of 1,2,3-tris (2-cyanoethoxy) propane were added.

Example  5

An electrolyte solution and a battery were prepared in the same manner as in Example 4, except that 1,2,3-tris (2-cyanoethoxy) propane was added in 4 parts by weight.

Example  6

An electrolyte solution and a battery were prepared in the same manner as in Example 4, except that 1,2,3-tris (2-cyanoethoxy) propane was added in 5 parts by weight.

Example  7

An electrolyte solution and a battery were prepared in the same manner as in Example 1, except that 3 parts by weight of vinylene carbonate and 3 parts by weight of 1,2,3-tris (2-cyanoethoxy) propane were added.

Example  8

An electrolyte solution and a battery were prepared in the same manner as in Example 7, except that 1,2,3-tris (2-cyanoethoxy) propane was added in 6 parts by weight.

Example  9

An electrolyte solution and a battery were prepared in the same manner as in Example 7, except that 1,2,3-tris (2-cyanoethoxy) propane was added at 9 parts by weight.

Comparative example  One

An electrolyte solution and a battery were prepared in the same manner as in Example 1, except that 1,2,3-tris (2-cyanoethoxy) propane was not added.

Comparative example  2

An electrolyte solution and a battery were prepared in the same manner as in Example 4, except that 1,2,3-tris (2-cyanoethoxy) propane was not added.

Comparative example  3

An electrolyte solution and a battery were prepared in the same manner as in Example 7, except that 1,2,3-tris (2-cyanoethoxy) propane was not added.

Comparative example  4

An electrolyte solution and a battery were manufactured in the same manner as in Example 6, except that 5 parts by weight of succinonitrile (SN) was added instead of 5 parts by weight of 1,2,3-tris (2-cyanoethoxy) propane. It was.

1. In high temperature conditions Swelling ( swelling ) Measure

The swelling evaluation was performed at high temperature conditions of each of the batteries prepared in Examples 1 to 9 and Comparative Examples 1 to 4 as follows.

After charging each cell to 4.20V, it was heated to 90 ° C. at an elevated temperature rate of 1 ° C./min at room temperature, and stored at 90 ° C. for 4 hours, and then the test was performed under conditions of decreasing the temperature to room temperature for 1 hour.

In the test, the swelling result was expressed as the maximum thickness change (ΔT) relative to the initial thickness, and the results are shown in Table 1 and FIG. 1.

Additive (part by weight) Thickness change (ΔT / μm) VC 3-CEP FEC SN Example 1 One One 3 0 317 Example 2 One 2 3 0 28 Example 3 One 3 3 0 0 ¹⁾ Example 4 2 2 3 0 415 Example 5 2 4 3 0 51 Example 6 2 5 3 0 0 Example 7 3 3 3 0 409 Example 8 3 6 3 0 262 Example 9 3 9 3 0 0 Comparative Example 1 One 0 3 0 1320 Comparative Example 2 2 0 3 0 1648 Comparative Example 3 3 0 3 0 1947 Comparative Example 4 2 0 3 5 448

¹⁾ : The thickness change of a battery whose swelling was not swelled due to the weight of the plate thickness meter but had a negative value was expressed as zero.

As shown in Table 1, it can be seen that the battery of the embodiments according to the present invention is superior to the bulging prevention effect than the battery of the comparative examples.

In particular, in comparison with Example 6 and Comparative Example 4, the 1,2,3-tris (2-cyanoethoxy) propane according to the present invention has a swelling inhibitory effect at high temperature storage conditions than succinonitrile, which is a similar nitrile compound It can be seen that excellent.

2. In high temperature conditions Charging and discharging  Cycle life measurement

The batteries prepared in Example 6 and Comparative Example 4 were subjected to charge / discharge cycle tests at a voltage range of 3.0 V to 4.2 V at 45 ° C., and the results are shown in Table 2 and FIG. 2 as capacity retention rates for initial capacities. It was.

Capacity maintenance rate (%) Cycle count Example 6 90.1 400 Comparative Example 4 87.5 400

As can be seen in Table 2, it can be seen that the 1,2,3-tris (2-cyanoethoxy) propane according to the present invention has an effect of improving the charge and discharge cycle life at a higher temperature than succinonitrile.

Claims (14)

In the nonaqueous electrolyte solution for lithium secondary batteries containing an ionizable lithium salt and an organic solvent,
The nonaqueous electrolyte,
(a) 1 to 10 parts by weight of a vinylene group or a compound containing a vinyl group based on 100 parts by weight of the total nonaqueous electrolyte; And
(b) 10 parts by weight to 300 parts by weight of a multinitrile compound having an ether bond represented by the following Chemical Formula 1 based on 100 parts by weight of the vinylene group or a compound containing a vinyl group:
[Formula 1]

In Chemical Formula 1,
R ¹ , R ² , R ³ and R ⁴ are each independently alkylene or alkenylene having 1 to 5 carbon atoms,
At least one of R ⁵ and R ⁶ is a nitrile bonded to a heteroalkyl group having 1 to 10 carbon atoms containing oxygen or sulfur, and the remainder is halogen or alkyl, alkenyl, alkylamine or aryl having 1 to 10 carbon atoms. The method of claim 1,
The vinylene group or the compound containing a vinyl group is any one selected from the group consisting of a vinylene carbonate compound, an acrylate compound containing a vinyl group, a sulfonate compound containing a vinyl group, and an ethylene carbonate compound containing a vinyl group. Or a mixture of two or more thereof. A nonaqueous electrolyte solution for a lithium secondary battery. The method of claim 1,
The compound containing the vinyl group is a non-aqueous electrolyte lithium secondary battery, characterized in that represented by the formula (2):
(2)

In Formula 2,
Of _{R 1, R 2, R 3} , R 4 , at least one of which contains a vinyl group, and the remains are each independently substituted with hydrogen, halogen, halogen or unsubstituted C alkyl group of _{1 ~ C 6, C 6 ~} C 12 an aryl group, an alkenyl group, or sulfonate group of C ₂ ~ C _6. The method of claim 1,
The multinitrile compound having an ether bond is 1,2,3-tris (2-cyanoethoxy) propane, 1,1,1-tris (cyanoethoxymethyl) ethane, 1,3-bis (2- Cyanoethoxy) -2,2-bis (2-cyanoethoxymethyl) propane and 3,3-[[2-[(2-cyanoethoxy) methyl] -2-ethyl-1,3 propane Diyl] bis (oxy)] bis [propanenitrile] is any one selected from the group consisting of, or a mixture of two or more thereof. The method of claim 1,
The non-aqueous electrolyte is a non-aqueous electrolyte lithium secondary battery, characterized in that further comprises a cyclic carbonate substituted with halogen represented by the formula (3):
(3)

In Chemical Formula 1,
X and Y are each independently hydrogen, chlorine, or fluorine, and X and Y are not simultaneously hydrogen. The method of claim 5,
The cyclic carbonate substituted with the halogen is a non-aqueous electrolyte solution for lithium secondary batteries, characterized in that the mixed content with the vinylene group or a compound containing a vinyl group is 1 to 10 parts by weight relative to 100 parts by weight of the nonaqueous electrolyte. The method of claim 1,
The lithium salt of the anion is ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, AlO 4 -, AlCl 4 -, PF 6 -, SbF 6 _{^{-, AsF 6 -, BF 2}} C 2 O 4 -, BC 4 O 8 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3 _{^{) 5 PF -, (CF 3}} ) 6 P -, CF 3 SO 3 -, C 4 F 9 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 _{^{N -, CF 3 CF 2 (}} CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 _{^{SO 3 -, CF 3 CO 2}} -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^-Non- aqueous electrolyte solution for a lithium secondary battery, characterized in that any one selected from the group consisting of. The method of claim 1,
The organic solvent is any one selected from the group consisting of ethers, esters, linear carbonates and cyclic carbonates, or a mixture of two or more thereof. 9. The method of claim 8,
The cyclic carbonates are ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate and their halides Non-aqueous electrolyte solution for a lithium secondary battery comprising any one selected from the group consisting of or a mixture of two or more thereof. 9. The method of claim 8,
The linear carbonate is lithium secondary, characterized in that it contains any one or a mixture of two or more selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate and ethylpropyl carbonate Non-aqueous electrolyte solution for batteries. 9. The method of claim 8,
The ether is any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether and ethylpropyl ether, or a mixture of two or more thereof. Nonaqueous electrolyte. 9. The method of claim 8,
The esters are methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone Non-aqueous electrolyte solution for lithium secondary batteries comprising any one selected from the group consisting of or a mixture of two or more thereof. In a lithium secondary battery comprising a negative electrode, a positive electrode and a nonaqueous electrolyte,
The nonaqueous electrolyte is a lithium secondary battery, characterized in that the nonaqueous electrolyte for lithium secondary battery of any one of claims 1 to 12. The method of claim 13,
The negative electrode is a lithium secondary battery characterized in that it comprises an aqueous binder.

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