KR101565533B1 - 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. The non-aqueous electrolyte solution for a lithium secondary battery of the present invention comprises an ionizable lithium salt; Organic solvent; And phenylbenzonitrile compounds of particular structure. The lithium secondary battery having the non-aqueous electrolyte of the present invention improves the safety and the cycle life and the high-temperature storage characteristics, and is particularly useful in a high-voltage battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte for a lithium secondary battery, and a lithium secondary battery having the same. 2. Description of the Related Art Non-aqueous electrolytes for lithium secondary batteries,

The present invention relates to a nonaqueous electrolyte for a lithium secondary battery and a lithium secondary battery having the same. More particularly, the present invention relates to a nonaqueous electrolyte for a lithium secondary battery containing a phenylbenzonitrile-based additive and having improved safety, cycle life and high-temperature storage characteristics, and a lithium secondary battery having the same.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs, and electric vehicles further expand, there is a growing demand for higher energy density of batteries used as power sources for such electronic devices. Lithium secondary batteries are the ones that can best meet these demands, and researches on them are actively under way.

Among the currently applied secondary batteries, the lithium secondary batteries developed in the early 1990s include a cathode made of a carbon material capable of absorbing and desorbing lithium ions, a cathode made of a lithium-containing oxide, and a mixed organic solvent, And a non-aqueous electrolytic solution.

Recently, as the use of lithium secondary batteries has expanded, demand for lithium secondary batteries capable of maintaining excellent performance even in harsh environments such as high temperature and low temperature environment and capable of being safely charged even at a high voltage is increasing.

However, the structural stability and the capacity of the lithium transition metal oxide or composite oxide used as the cathode active material of the lithium secondary battery are determined by the occlusion and release of lithium ions. The capacity of the lithium transition metal oxide or complex oxide increases as the charge potential increases. The emission of the transition metal and the like is also accelerated and structural instability may be caused. Nevertheless, as the application range of lithium secondary batteries has expanded, there is a growing demand for lithium secondary batteries to be used even in harsh environments such as high temperature, low temperature environment, and high voltage charging.

Currently, organic solvents widely used in non-aqueous electrolytic solutions include ethylene carbonate, propylene carbonate, dimethoxyethane, gamma butyrolactone, N, N-dimethylformamide, tetrahydrofuran or acetonitrile. When stored at a high temperature for a long time, the stable structure of the battery may be deformed due to the generation of gas due to the oxidation of the electrolyte, or the battery may be ignited or exploded during internal heating due to overcharging.

For example, as the voltage increases during overcharging, the electrolyte becomes unstable due to excessive lithium ion emission from the anode, and the electrolyte decomposes due to the oxidative exothermic reaction between the anode and the electrolyte in this state. In the cathode, lithium precipitation occurs and the reaction with the electrolyte increases. These reactions cause an exothermic reaction which results in a sudden increase in the temperature of the battery, which may cause ignition and explosion.

In order to improve the overcharge safety, JP-A-9-106835 uses biphenyl which is capable of electrochemical polymerization. However, biphenyl has a low solubility with respect to a polar electrolyte and has a problem that the polymerization reaction occurs even when charging / discharging is continued up to the upper limit of the voltage of 4.2 V or when the battery is stored at a high temperature of about 50 캜 or more, .

Accordingly, an object of the present invention is to provide a nonaqueous electrolyte for a lithium secondary battery and a lithium secondary battery having the same, which can improve not only the overcharge safety of the electrolyte, but also the cycle characteristics at a high temperature and the high temperature storage performance .

In order to solve the above problems, the non-aqueous electrolyte solution for a lithium secondary battery of the present invention comprises an ionizable lithium salt; Organic solvent; And a phenylbenzonitrile compound represented by the following formula (1): < EMI ID =

In Formula 1,

At least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ and R ₁₀ is a nitrile group and the rest is an alkyl group having 1 to 3 hydrogen, , At least one of R ₃ and R ₈ is hydrogen or an alkyl group having 1 to 3 carbon atoms.

In the nonaqueous electrolyte solution of the present invention, the phenylbenzonitrile compound may be used alone or in combination of two or more of 4-biphenylcarbonitrile, 4-cyano-4'-methylbiphenyl, 3-cyanobiphenyl, But they are not limited thereto. The phenylbenzonitrile compound may be contained in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte.

In the non-aqueous liquid electrolyte of the present invention, the lithium salt ^{anion, 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 ^- , (CF ₃ CF ₂ SO ₂ ) ₂ N ^- and the like.

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

In the nonaqueous electrolyte according to the present invention, the phenylbenzonitrile compound according to the present invention forms a conductive film on the surface of the anode, thereby suppressing the decomposition reaction of the electrolytic solution, thereby improving the safety of the battery during overcharging. In addition, it has excellent effect of suppressing deterioration of cell performance due to generation of gas upon storage at a high temperature while maintaining excellent cycle characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
FIG. 1 is a graph of an LSV (Linear Sweep Voltammetry) obtained by measuring a reaction initiation voltage of an electrolyte with respect to the battery of Example 1 of the present invention. FIG.
2 is a graph of LSV (Linear Sweep Voltammetry) obtained by measuring a reaction initiation voltage of an electrolyte for the battery of Comparative Example 1 of the present invention.

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

As described above, when the battery is overcharged, lithium ions are excessively discharged from the anode, and the structure of the cathode active material becomes more unstable. Oxygen is released from the cathode active material with unstable structure, Decomposition reaction proceeds. In addition, at high temperature conditions, the dissolution of metal ions in the positive electrode is increased, and such metal ions are precipitated on the negative electrode, thereby further promoting the problem of deterioration of battery performance.

Accordingly, the present invention relates to an ionizable lithium salt; Organic solvent; And a phenylbenzonitrile compound represented by the following general formula (1), to solve the above problems.

[Chemical Formula 1]

In Formula 1,

At least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ and R ₁₀ is a nitrile group and the rest is an alkyl group having 1 to 3 hydrogen, , At least one of R ₃ and R ₈ is hydrogen or an alkyl group having 1 to 3 carbon atoms.

The phenylbenzonitrile compound according to the present invention is considered to form a conductive film by performing a polymerization reaction at the surface of the anode when a predetermined voltage is reached during charging and discharging. This conductive film prevents the dispersion of metal ions eluted from the cathode active material and prevents the contact between the anode and the electrolytic solution to inhibit the decomposition reaction of the electrolytic solution. Therefore, the safety during overcharging can be improved and the decomposition reaction of the electrolytic solution can be effectively suppressed even at high temperature storage. In addition, since the film formed by the phenylbenzonitrile compound according to the present invention has conductivity, the cycle characteristics of the battery can be maintained excellent.

Specific examples of the phenylbenzonitrile compound represented by the formula (1) include 4-biphenylcarbonitrile, 4-cyano-4'-methylbiphenyl, 3-cyanobiphenyl and 2-cyanobiphenyl Or a mixture of two or more of them, but the present invention is not limited thereto.

The phenylbenzonitrile compound according to the present invention is preferably contained in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the non-aqueous electrolyte. If the content is less than 0.5 parts by weight, the effect of stabilizing the SEI film is insufficient. If the content is more than 5 parts by weight, the resistance increase effect due to the alkyl chain of the phenylbenzonitrile compound is substantially exhibited.

In this respect, the phenylbenzonitrile compound according to the present invention is more preferably contained in the non-aqueous electrolyte at 1 to 5 parts by weight.

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 - there can be mentioned any one selected from the group consisting of.

Examples of the organic solvent included in the non-aqueous electrolyte of the present invention include those conventionally used for an electrolyte for a lithium secondary battery without limitation, and examples thereof include ether, ester, amide, linear carbonate, cyclic carbonate, Two or more of them may be used in combination.

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 halides thereof, or a mixture of two or more thereof. Specific examples of the linear carbonate compound include a group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate Any one selected, or a mixture of two or more thereof may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high viscosity organic solvent and dissociate the lithium salt in the electrolyte well, and dimethyl carbonate and diethyl carbonate When a low viscosity and a low dielectric constant linear carbonate are mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

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 linear esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate; And cyclic esters such as? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone and? -Caprolactone, or a mixture of two or more thereof However, the present invention is not limited thereto.

The nonaqueous electrolyte solution for a lithium secondary battery of the present invention described above is manufactured as a lithium secondary battery by injecting it into an electrode structure composed of 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 constituting the electrode structure may be any of those conventionally used in the production of lithium secondary batteries.

As a specific example, the cathode active material include lithium-containing transition and the metal oxide is preferably used, for example, _{Li x CoO 2 (0.5 <x} <1.3), Li x NiO 2 (0.5 <x <1.3), 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 < 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 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), or a mixture of two or more thereof. The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide . In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

As the anode active material, a carbon material, lithium metal, silicon or tin, which lithium ions can be occluded and released, can be used, and metal oxides such as TiO ₂ and SnO ₂ having a potential with respect to lithium of less than ₂ V are also possible. Preferably, carbon materials can be used, and carbon materials such as low-crystalline carbon and highly-crystalline carbon can be used. Examples of the low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber high temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

The anode and / or the cathode may include a binder, and examples of the binder include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile ), Polymethylmethacrylate, and the like can be used.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, a polyolefin such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer A porous polymer film made of a high molecular weight polymer may be used alone or in a laminated manner, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, a 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 a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like 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

&Lt; Preparation of non-aqueous electrolyte &

1 part by weight of 4-biphenylcarbonitrile was further added to 100 parts by weight of a mixed solvent having a composition of ethylene carbonate: propylene carbonate: ethyl propionate = 2: 1: 7 (weight ratio), and then LiPF ₆ was added To prepare a non-aqueous electrolyte.

<Manufacture of Battery>

LiCoO ₂ as a cathode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive material were mixed at a weight ratio of 96: 3: 3, and then dispersed in N-methyl-2-pyrrolidone to prepare a cathode slurry The slurry was coated on an aluminum current collector, followed by drying and rolling to prepare a positive electrode.

Further, a negative electrode slurry was prepared by mixing artificial graphite as a negative electrode active material, styrene-butadiene rubber as a binder and carboxymethyl cellulose as a binder in a weight ratio of 97: 1.5: 1.5 and then dispersing in water to prepare an anode slurry. Coated, dried and rolled to prepare a negative electrode.

Thereafter, the prepared anode and anode were combined with a PE separator to produce a 18650 cylindrical cell by a conventional method, and then the electrolyte was injected to complete the cell preparation.

Example  2

A non-aqueous electrolyte and a battery were prepared in the same manner as in Example 1, except that 2 parts by weight of 4-biphenylcarbonitrile was added.

Example  3

A nonaqueous electrolytic solution and a battery were prepared in the same manner as in Example 1, except that 2-cyanobiphenyl was used as the phenylbenzonitrile compound.

Example  4

A non-aqueous electrolyte and a battery were prepared in the same manner as in Example 1, except that 3-cyanobiphenyl was used as the phenylbenzonitrile compound.

Comparative Example  One

An electrolyte and a battery were prepared in the same manner as in Example 1, except that 4-biphenylcarbonitrile was not added.

Comparative Example  2

A nonaqueous electrolytic solution and a battery were prepared in the same manner as in Example 1, except that 2 parts by weight of biphenyl was added instead of 4-biphenylcarbonitrile.

Test Example  1: Measurement of capacity retention rate at high temperature

The cells prepared in Examples and Comparative Examples were charged in a 50 ° C chamber at 0.8 C rate to 4.35 V under a constant current / constant voltage condition and charged at 0.05 C cut off, and discharged at 0.5 C 3.0 V. Respectively.

The ratio of the discharge capacity after each cycle was calculated based on the discharge capacity after one cycle, and the results are shown in Table 1.

50 ℃ Capacity retention rate After 100 cycles After 300 cycles Example 1 91% 80% Example 2 90% 79% Example 3 91% 80% Example 4 91% 80% Comparative Example 1 89% 79% Comparative Example 2 87% 75%

As shown in Table 1, it can be confirmed that the capacity retention ratios of Examples 1 to 4 are superior to those of Example 2 in comparison with the case of adding biphenyl, which is a conventional overcharge protection agent, which is not phenylbenzonitrile of the present invention.

The cell of Comparative Example 1 exhibits capacity retention performance similar to those of the Examples but exhibits undesirable results in subsequent performance tests.

Test Example  2: High-temperature storage performance measurement

The cells prepared in Examples and Comparative Examples were charged at a constant current / constant voltage of 4.35 V at a rate of 0.8 C and charged at a cut off rate of 0.05 C, and then stored in a 75 ° C chamber.

The voltage of each cell was measured with time, and the results are shown in Table 2.

75 ℃ chamber storage day After 5 days After 10 days After 30 days Example 1 4.20 4.16 4.03 Example 2 4.20 4.15 4.02 Example 3 4.20 4.16 4.03 Example 4 4.20 4.16 4.03 Comparative Example 1 4.08 X - Comparative Example 2 4.15 4.09 -

As shown in Table 2, it can be seen that CID short-circuit occurred at 10 days after the comparison, and that the voltage drop of the battery of Comparative Example 2 was larger than those of the Examples.

Test Example  3: overcharge safety measurement

The cells prepared in Examples and Comparative Examples were charged at a constant current / constant voltage of 4.35 V at 0.8 C rate and charged at 0.05 C cut off, and discharged at 0.5 C 3.0 V. Thereafter, overcharge of 0.8C 10V was performed again. After overcharging, the battery was evaluated as OK only when there was no ignition, explosion, and electrolyte leakage. The results are shown in Table 3 below.

Example 1 OK Example 2 OK Example 3 OK Example 4 OK Comparative Example 1 X Comparative Example 2 OK

As shown in Table 3, it can be confirmed that the battery of Comparative Example 1 in which no additive is used has insufficient overcharge safety compared to other batteries.

Test Example  4: Measurement of electrolyte decomposition initiation voltage

Aqueous electrolyte according to Example 2 and Comparative Example 2 were respectively used and platinum was used as a working electrode, lithium metal was used as a counter electrode and lithium metal was used as a reference electrode at 20 mV / s (Linear Sweep Voltammetry) was measured at a scan rate of 100 Hz and the results are shown in FIG. 1 (Example 2) and FIG. 2 (Comparative Example 2), respectively.

Referring to FIGS. 1 and 2, it can be seen that the oxidation starting voltage in the electrolyte solution of Example 2 is about 4.75 V, whereas the non-aqueous electrolyte solution of Comparative Example 2 is about 4.56 V in oxidation initiation voltage.

That is, it can be seen that the stability of the non-aqueous electrolyte according to the present invention is higher than that of the comparative example due to the higher starting voltage of the oxidative decomposition reaction. In particular, since the oxidation voltage is lowered in a high temperature environment, The characteristics are better than those of the comparative example.

Claims (10)

Ionizable lithium salts;
Organic solvent; And
A mixture of two or more selected from the group consisting of 4-biphenylcarbonitrile, 4-cyano-4'-methylbiphenyl, 3-cyanobiphenyl and 2-cyanobiphenyl, Non-aqueous electrolyte for secondary battery.
delete The method according to claim 1,
The mixture of any one selected from the group consisting of 4-biphenecarbonitrile, 4-cyano-4'-methylbiphenyl, 3-cyanobiphenyl and 2-cyanobiphenyl, or a mixture of two or more thereof, 0.5 to 5 parts by weight based on 100 parts by weight of the nonaqueous electrolyte solution for a lithium secondary battery. The method according to 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 lithium secondary battery, characterized in that at least one selected from the group consisting of. The method according to claim 1,
Wherein the organic solvent includes any one selected from the group consisting of an ether, an ester, an amide, a linear carbonate, and a cyclic carbonate, or a mixture of two or more thereof. 6. The method of claim 5,
The cyclic carbonate may be at least one selected from the group consisting of ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, , Or a mixture of two or more thereof. The nonaqueous electrolyte solution for a lithium secondary battery according to claim 1, 6. The method of claim 5,
Wherein the linear carbonate comprises any one selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, or a mixture of two or more thereof. Non-aqueous electrolyte for batteries. 6. The method of claim 5,
Wherein the ether includes 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. Non-aqueous electrolyte. 6. The method of claim 5,
The ester may be selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone and? -Caprolactone, or a mixture of two or more thereof. A lithium secondary battery comprising a negative electrode, a positive electrode and a non-aqueous electrolyte,
The lithium secondary battery according to any one of claims 1 to 9, wherein the non-aqueous electrolyte is a non-aqueous electrolyte for a lithium secondary battery.

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