KR100859999B1 - Cyclic Cyano Carbonate Compound, and Non-aqueous Electrolyte System Containing the Same as an Additive, and Lithium Secondary Battery of Improved Safety Having the Same - Google Patents

Abstract

The present invention is a ring of formula (1) that can minimize the phenomenon when the local short circuit occurs due to the physical impact applied from the outside of the battery in the charging or overcharge state, or the ignition and rupture caused by the temperature rise inside the battery By using the cyano carbonate compound and the electrolyte additive, the amount of heat generated by the reaction between the positive electrode and the electrolyte is reduced to prevent ignition and rupture of the battery, thereby providing a lithium secondary battery having improved safety.

Description

Cyclic Cyano Carbonate Compound, and Non-aqueous Electrolyte System Containing the Same as an Additive, and Lithium Secondary Battery of Improved Safety Having the Same}             

1 is a graph showing an exothermic temperature peak and an exothermic control result of a positive electrode measured in a battery manufactured through Example 1 and Comparative Example 1, respectively;

2A and 2B are graphs showing results of 160 ° C. high temperature exposure experiments (voltage and temperature) of batteries prepared through Examples 1 and 2, respectively;

3A to 3C are graphs showing the results of 12 V / 1 C overcharge experiments (voltage and temperature) of the batteries prepared through Example 1, Example 2, and Comparative Example 1, respectively;

Figures 4a to 4c is a graph showing the results of the 10 V / 1 A overcharge test (voltage, temperature) of the battery prepared through Example 1, Example 2 and Comparative Example 1, respectively.

The present invention relates to a non-aqueous lithium secondary battery, and more particularly, a local short circuit occurs due to a physical shock applied from the outside of the battery in a charged or overcharged state, or ignition and rupture due to a temperature rise inside the battery. When occurring, the cyclic cyano carbonate compound of Formula 1, which can minimize the phenomenon, and the additive as an electrolyte additive, reduce the amount of heat generated by the reaction between the positive electrode and the electrolyte to prevent ignition and rupture of the battery. Provided is an improved non-aqueous lithium secondary battery.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches have been conducted and commercialized on lithium secondary batteries with high energy density and high discharge voltage. It is widely used.

However, since lithium secondary batteries have high operating potentials, high energy may flow instantaneously, and a dendrite phase of lithium metal is formed on the surface of a negative electrode, thereby degrading the stability of the battery. In addition, since the positive electrode materials used in the battery greatly increase the chemical activity during overcharging, there is a possibility that the internal pressure of the battery increases rapidly by generating a large amount of gas by rapidly reacting with the electrolyte, and in some cases, the battery itself may explode. . Therefore, many studies on the safety of the battery are in progress.

In general, as a method for evaluating the safety of a battery, a safety evaluation is performed in which a battery is heated at a constant rate and exposed to a high temperature for an appropriate time in an oven capable of convection, in which case the cathode active material is The exothermic reaction by exothermic decomposition and the reaction of the non-aqueous electrolyte and the active material proceeds, resulting in thermal runaway due to the local temperature rise inside the battery, causing the battery to ignite and burst.

In order to prevent such a phenomenon, an exothermic reaction between the electrolyte solution and the positive electrode active material is carried out by using a flame retardant organic solvent in place of the non-aqueous electrolyte that is a flammable organic solvent used in a conventional secondary battery, or by adding a material having high temperature safety to an existing nonaqueous electrolyte. A method has been proposed to prevent the battery from igniting and exploding due to thermal runaway due to rapid heat generation. For example, a technique is disclosed in which an electrolyte solution contains a phosphate ester having a self-extinguishing property or a phosphate ester compound substituted with a halogen. Or the technique which improves safety by raising a flash point using a fluorine-substituted compound or a chlorine-substituted compound in electrolyte solution itself is proposed.

However, when the electrolytic solution contains a self-extinguishing substance or a substance having a high flash point, there is a problem that the ionic conductivity of the electrolytic solution is lowered and the high rate discharge characteristics and the low temperature characteristics of the battery are lowered. In addition, even if a technique containing a microcapsule containing a flame retardant or a chemical that causes an electrolyte curing reaction is used, the combustion of the electrolyte is accelerated by the oxygen released from the electrode during the thermal safety test by heating, leading to ignition. Therefore, there is a problem that does not provide reliable safety.

 Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After extensive research and various experiments, the inventors have developed a cyclic cyano carbonate compound, which is a new compound, as described later, and by adding the compound to the electrolyte solution, the battery is internally shorted or heated. It has been found that even when exposed to high temperature due to the temperature increase by the present invention, a stable secondary battery capable of preventing ignition and bursting can be prevented. The present invention has been completed based on this finding.

Specifically, the first object of the present invention is to provide a cyclic cyano carbonate compound of formula (1).

A second object of the present invention is to provide a non-aqueous electrolyte containing the compound as an electrolyte additive.

A third object of the present invention is to provide a lithium secondary battery having improved safety using the non-aqueous electrolyte as a component.

Cyclic carbonate compound according to the present invention for achieving this object is represented by the following formula (1).                     

[Formula 1]

Where

X is selected from the group consisting of hydrogen, lower alkyl group and cyano group;

Z is selected from the group consisting of hydrogen, cyano group, halogen, nitro group and substituted or unsubstituted linear, branched or cyclic alkyl group;

n is an integer from 1 to 10;

R is selected from the group consisting of hydrogen, cyano group, halogen, nitro group, substituted or unsubstituted linear, branched or cyclic alkyl group and (CH (-X)) _n Z, wherein X, Z and n are The same as each definition of;

At least one of X, Z and R is a cyano group or contains a cyano group.

In Formula 1, X is preferably hydrogen, Z is preferably a cyano group, and R is preferably (CH (-X)) _n Z.

As an example of the compound of Formula 1, the compound of Formula 2a or Formula 2b is preferable.                     

[Formula 2a]

[Formula 2b]

Where

X is selected from the group consisting of hydrogen, lower alkyl group and cyano group;

Z is selected from the group consisting of hydrogen, cyano group, halogen, nitro group and substituted or unsubstituted linear, branched or cyclic alkyl group;

n is an integer from 1 to 10;

At least one of X and Z is a cyano group.

In Formulas 2a and 2b, X is preferably hydrogen, and Z is preferably a cyano group. Representative examples of the compound include 1,4-dicyano-2,3-butylene carbonate (1,4-dicyano-2,3-butylene carbonate) represented by the following Chemical Formula 3.                     

[Formula 3]

C ₇ H ₆ N ₂ O ₃ (exact mass: 166.04, mol.wt .: 166.13, solid)

The cyclic cyano carbonate compound according to the present invention can be prepared by various methods, and typically 1,4-dicyano-2,3-butylene carbonate of Chemical Formula 3 is prepared by the following Scheme 1. Can be.

Scheme 1

1) Synthesis scheme 1

2) synthesis scheme 2

The present invention also provides a lithium salt-containing non-aqueous electrolyte containing the compound of Formula 1 as a stabilizing additive.

The content of the compound of Formula 1 is 10% by weight or less, more preferably 5% by weight or less based on 100% by weight of the non-aqueous electrolyte. When the content is 10% by weight or more, the performance of the battery is lowered, which is not preferable.

The said lithium salt containing non-aqueous electrolyte consists of a nonaqueous electrolyte and lithium. As the nonaqueous electrolyte, a nonaqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

As said non-aqueous electrolyte, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Low lactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, aceto Nitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative Aprotic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyroionate and ethyl propionate can be used.

Examples of the organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, poly-edgetion lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and ionic dissociation groups. Containing polymers and the like can be used.                     

As the inorganic solid electrolyte, for example, Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides, sulfates, and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may be used.

The lithium salt is a good material to be dissolved in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide have.

In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, etc. Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, etc. It may be. In some cases, in order to impart nonflammability, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics.

The present invention also provides

a) a cathode capable of occluding and releasing lithium ions;

b) a negative electrode capable of occluding and releasing lithium ions;                     

c) a porous separator; And

d) an electrolyte comprising a lithium salt, a nonaqueous electrolyte and a cyclic cyano carbonate of formula (1);

It provides a lithium secondary battery comprising a.

The lithium secondary battery, unlike the conventional one, contains a cyclic cyano carbonate of Formula 1 in addition to containing a lithium salt and a non-aqueous electrolyte to alleviate thermal runaway generated inside the battery to provide a non-aqueous secondary battery having excellent safety. It is characterized by providing.

That is, the secondary battery of the present invention containing the compound in the electrolyte, the electrode (particularly at high temperatures or local short-circuit due to external physical shock (for example, when exposed to high temperature by heating) when the battery is charged or overcharged) Ignition and rupture of the battery due to the combustion and thermal runaway of the electrolyte by oxygen generated from the positive electrode), and the compound absorbs / discharges heat generated during internal short circuit or high temperature exposure. Oxygen released when the anode collapses above a certain temperature (eg, 160 ° C. or higher) accelerates combustion of the electrolyte and prevents ignition or rupture due to thermal runaway.

Hereinafter, other components of the secondary battery according to the present invention will be described in detail.

The positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive agent, and a binder onto a positive electrode current collector, followed by drying, and optionally, a filler is further added to the mixture.

The positive electrode current collector is generally made to a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver, or the like may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The conductive agent is typically added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive agent include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. In some cases, since the conductive second coating layer is added to the positive electrode active material, the addition of the conductive agent may be omitted.

The binder is a component that assists in bonding the active material and the conductive agent to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.                     

The negative electrode is manufactured by applying and drying a negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The negative electrode current collector is generally made to a thickness of 3 to 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface treated with carbon, nickel, titanium, silver, and the like, and aluminum-cadmium alloys. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material may be, for example, carbon such as hardly graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ _x ≦ 1), Li _x WO ₂ (0 ≦ _x ≦ 1), Sn _x Me _1-x Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me' Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally from 0.01 to 10 ㎛ ㎛, thickness is generally 5 ~ 300 ㎛. As such a separator, for example, olefin polymers such as chemical resistance and hydrophobic polypropylene; Sheets or non-woven fabrics made of glass fibers or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.

The lithium secondary battery according to the present invention can be produced by conventional methods known in the art. That is, it may be prepared by inserting a porous separator between the anode and the cathode and injecting an electrolyte therein.

The positive electrode may be manufactured by, for example, applying a slurry containing the lithium transition metal oxide active material, the conductive material, and the binder described above onto a current collector and then drying. Similarly, the negative electrode can be prepared by, for example, applying a slurry containing the above-described carbon active material, a conductive material and a binder onto a thin current collector and then drying it.

In the lithium secondary battery according to the present invention, the structure of the positive electrode, the negative electrode, and the separator is not particularly limited. For example, each of these sheets may be wound, wound, or stacked in a cylindrical, rectangular, or pouch type. It may be inserted into the case of the mold.

Hereinafter, the contents of the present invention will be described in detail through production examples, examples, and comparative examples, but the scope of the present invention is not limited thereto.

[Production Example 1]

Preparation of 1,4-dicyano-2,3-butylene carbonate

(1) Preparation of 3,4-Dihydroxyhexanedinitrile

Osmium tetroxide in a solution containing 4 g of 1,4-dicyano-2-butene and 8.8 g of NMO (N-Methylmorpholine-N-oxide) in 120 ml of acetone / H ₂ O (4/1: v / v) mixed solvent 9.6 ml (4% in H ₂ O) were added. The reaction solution was stirred under cool conditions (0 ° C). Then, the mixture was diluted with 80 ml of Ethyl acetate, and 50 ml of saturated aqueous sodium sulfite solution was added to separate the organic layer. The aqueous layer was extracted twice with Ethyl acetate, and the organic layers were collected, dried over anhydrous magnesium sulfate, filtered and concentrated. Finally, the residue was purified by flash column chromatography to obtain 4.81 g of the title compound.

¹ H NMR (DMSO), δ 2.59 (2H), 2.59 (2H), 3.70 (1H), 3.70 (1H)

(2) Preparation of 1,4-dicyano-2,3-butylene carbonate

4.66 g of Triphosgene, 30 ml of Dichloromethane and 5 ml of Pyridine were cooled to 0 ° C., and a solution obtained by dissolving the compound (2 g) prepared in Step (1) in 10 ml of Dichloromethane was slowly added to the mixed solution. Stirred. After 4 hours, the reaction was stopped using saturated aqueous solution of Ammonium chloride. Then, the organic layer was separated and the aqueous layer was extracted with diethyl ether.                     

After extraction, the combined organic layers were washed with saturated aqueous sodium bicarbonate and brine, dried over anhydrous sodium sulfate, and purified by flash column chromatography to obtain 2.14 g of the title compound.

¹ H NMR (DMSO), δ 3.21 (2H), 3.21 (2H), 4.83 (1H), 4.83 (1H),

¹³ C NMR (CD ₃ COCD ₃ ), δ 153.4 (-C = O, s), 116.6 (-CN, s), 76.8 (-CHO-, s), 22.9 (-CH _2- , s).

Example 1

As an electrolyte, an EC: EMC = 1: 1 (weight%) solution was used, and LiPF ₆ was used as a lithium salt, 1M, and 1,4-dicyano-2,3-butylene carbonate synthesized in Preparation Example 1 was used herein. 3 wt% was added. Artificial graphite was used as the negative electrode active material, and LiCoO ₂ was used as the positive electrode active material. Then, a 323456 type lithium polymer battery was manufactured by a conventional method, and a battery was manufactured using an aluminum laminate packaging material.

Example 2

A battery was manufactured in the same manner as in Example 1, except that 5 wt% of 1,4-dicyano-2,3-butylene carbonate was added to the electrolyte.

Comparative Example 1

A lithium polymer battery was manufactured in the same manner as in Example 1, except that 1,4-dicyano-2,3-butylene carbonate was not added to the electrolyte.

Experimental Example 1

Measurement of the exothermic change of anode according to temperature change

The calorific values of the batteries prepared in Example 1 and Comparative Example 1 were measured using a DSC apparatus while the temperature was raised to 350 ° C. at 5 ° C./min. The results are shown in FIG. 1, which shows an exothermic temperature peak and an exothermic control result of the anode, and it can be seen that enthalpy is significantly reduced compared to Comparative Example 1.

Experimental Example 2

Hot Box Test

The batteries prepared in Example 1, Example 2 and Comparative Example 1 were prepared in a fully charged state. In the high temperature exposure experiment, the temperature was increased to 5 ° C./min in an oven capable of convection to expose a fully charged battery for 1 hour at a high temperature of 160 ° C. to confirm whether or not the battery was ignited. As shown in Table 1 below, the battery of Comparative Example 1 was ignited at a temperature of 160 ℃, it was confirmed that the battery of Example 1 and Example 2 has excellent safety by not igniting under the same conditions.

For reference, in the batteries of Examples 1 and 2, changes in voltage with temperature change are shown in FIGS. 2A and 2B, respectively. Referring to these figures, it can be seen that the battery does not ignite without a voltage change in the high temperature exposure experiment.

Experimental Example 3

Overcharge test

3 and 4 show the results of overcharging and temperature changes of the batteries prepared in Examples 1, 2, and Comparative Example 1, respectively, in a constant current constant voltage (CCCV) method at 12V / 1C and 10V / 1A. Represented in each.

Specifically, the results of Example 1 are shown in FIG. 2A, the results of Example 2 are shown in FIG. 3B, and the experimental results of Comparative Example 1 are shown in FIG. 3C, respectively. In addition, the results of Example 1 are shown in FIG. 4A, the result of Example 2 is shown in FIG. 4B, and the experiment result of Comparative Example 1 is shown in FIG. 4C of the overcharge test result on 10V / 1A conditions, respectively.

Referring to these drawings, it can be seen that the safety at the time of overcharge of Examples 1 and 2 is improved than the battery of Comparative Example 1. That is, referring to FIGS. 3C and 4C of Comparative Example 1, the battery ignited and shorted while its maximum temperature was measured at about 170 ° C. due to the exothermic reaction resulting from the oxidation reaction of the electrolyte and the structural collapse of the positive electrode. . On the other hand, the secondary batteries of Examples 1 and 2 including the electrolyte solution containing the additive according to the present invention exhibits a maximum temperature of about 100 ° C. by controlling the exothermic reaction inside the battery. The average value of the overcharge experiments repeated several times is shown in Table 2 below.

As described above, when the cyclic cyano carbonate compound of the formula (1) according to the present invention is used as an electrolyte additive, it may be subjected to external physical shock (for example, during high temperature exposure by heating) in a charged or overcharged state. Ignition of the battery due to thermal runaway when the battery is overheated due to local short circuit or heat generation due to the reaction of the flammable electrolyte and the positive electrode active material at a high temperature, and the combustion of the electrolyte is accelerated by oxygen generated from the positive electrode and By controlling the rupture phenomenon can provide a secondary battery with improved high temperature safety of the battery.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (12)

delete delete delete delete delete delete delete A method for producing 1,4-dicyano-2,3-butylene carbonate (1,4-dicyano-2,3-butylene carbonate) by the following reaction. (One)

(2)

a) a cathode capable of occluding and releasing lithium ions; b) a negative electrode capable of occluding and releasing lithium ions; c) a porous separator; And d) an electrolyte comprising a lithium salt, a nonaqueous electrolyte, and 1,4-dicyano-2,3-butylene carbonate of the formula (3); Lithium secondary battery comprising a.

(3) The lithium secondary battery of claim 9, wherein the content of the compound of Formula 3 is 10 wt% or less based on 100 wt% of the non-aqueous electrolyte. delete 10. The lithium secondary battery of claim 9, wherein the battery is a cylindrical, square or pouch type battery.

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