KR20180019910A - Nonaqueous electrolytic solution and lithium secondary battery - Google Patents

Abstract

Provided are a nonaqueous electrolyte containing an amide compound having a cyanoalkyl group as an electrolyte additive, and a lithium secondary battery including the same. The lithium secondary battery using the nonaqueous electrolyte containing the electrolyte additive ensures excellent cycle lifespan properties by containing the electrolyte additive, extends lifespan of the battery, and increases discharge capacity.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery,

The present invention relates to a nonaqueous electrolyte containing an amide compound containing a cyanoalkyl group as an electrolyte additive and a lithium secondary battery comprising the same. More particularly, the present invention relates to a lithium secondary battery comprising an amide compound containing a cyanoalkyl group as an electrolyte additive, To provide a nonaqueous electrolyte having excellent life characteristics, prolonging the life of the battery, and increasing the discharge capacity, and a lithium secondary battery comprising the same.

In the lithium secondary battery, an electrolyte is interposed between the positive electrode and the negative electrode to enable smooth movement of lithium ions, and electricity is generated or consumed by redox reaction caused by insertion and desorption in the positive electrode and negative electrode.

Lithium secondary batteries, which are mainly used as power sources for mobile IT devices and power tools, such as mobile phones, are being used for applications such as automobiles and energy storage due to the development of large-capacity technologies.

As such an application field is widened and demand is increased, battery performance and stability that are better than those required in conventional small batteries are required. In recent years, battery characteristics such as output characteristics, cycle characteristics, storage characteristics, Various investigations have been made on organic solvents and additives as components for electrolytic solution.

It has been difficult to expect improvement in low-temperature output characteristics due to the formation of a non-uniform SEI film in the case of an electrolyte solution which does not contain an electrolyte additive or contains an electrolyte additive having poor characteristics. Further, even when the amount of the electrolyte additive is included, if the amount of the electrolyte additive can not be adjusted to the required amount, the surface of the anode may be decomposed or the oxidation reaction may occur at the high temperature due to the electrolyte additive, thereby ultimately increasing the irreversible capacity of the secondary battery, There is a problem in that it is lowered.

Patent Document 1: Korean Patent Publication No. 2015-0123746 Patent Document 2: Korean Patent Publication No. 2014-0033539

In order to solve the problems of the prior art as described above, it is an object of the present invention to provide an electrolyte having excellent cycle life characteristics, prolonging the life of the battery, and increasing the discharge capacity, and a lithium secondary battery comprising the same do.

These and other objects of the present invention can be achieved by the present invention described below.

In order to accomplish the above object, the present invention provides a nonaqueous organic solvent; Lithium salts; And an amide compound containing a cyanoalkyl group, wherein the amide compound containing a cyanoalkyl group is represented by the following formula (1)

[Chemical Formula 1]

(Wherein R ₁ and R ₃ are alkylene having 1 to 20 carbon atoms and R ₂ is hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, An arylalkyl group having 6 to 30 carbon atoms, and a cyanoalkyl group having 1 to 20 carbon atoms. The present invention also provides a nonaqueous electrolyte solution comprising the same.

According to such a nonaqueous electrolyte solution, a high capacity and a high initial charging / discharging efficiency, and gas generation inside the battery also constitute a nonaqueous electrolyte solution which is more safe and reliable than a conventional nonaqueous electrolyte secondary battery.

In addition, cathode; A separator; And a nonaqueous electrolytic solution,

Wherein the anode is a manganese spinel-based active material or a lithium metal oxide, and the cathode is a carbon-based anode active material selected from the group consisting of crystalline carbon, amorphous carbon, artificial graphite, and natural graphite, and the nonaqueous electrolyte is the above- A lithium secondary battery is provided.

By using the lithium secondary battery using the above-described electrolyte solution, it is possible to provide a lithium secondary battery having high safety and high reliability because it has a high capacity, excellent initial charge / discharge efficiency and cycle characteristics, and can reduce gas generation inside the battery .

According to the present invention, it is an object of the present invention to provide an electrolytic solution having excellent room temperature and high temperature service life characteristics, prolonging the life of the battery, and increasing the discharge capacity. Therefore, in the case of a lithium secondary battery including a positive electrode manufactured using the positive electrode, it is advantageous in that capacity can be increased and life characteristics of an excellent battery can be secured

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

The nonaqueous electrolyte solution of the present invention is a nonaqueous organic solvent; Lithium salts; And an amide compound containing a cyano alkyl group,

Wherein the amide compound containing the cyanoalkyl group is represented by the following formula (1)

[Chemical Formula 1]

(Wherein R ₁ and R ₃ are alkylene having 1 to 20 carbon atoms and R ₂ is hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, An arylalkyl group having 6 to 30 carbon atoms, and a cyanoalkyl group having 1 to 20 carbon atoms).

The amide compound containing the cyanoalkyl group is included as an additive in the non-aqueous electrolyte, and when the lithium secondary battery is constituted, the lithium salt is decomposed into HF when stored at high temperature, or COx is generated by decomposition of EC in a non-aqueous organic solvent The secondary battery can be provided with a high capacity and a small amount of gas generation inside the battery, thereby providing a secondary battery with high safety and reliability.

Specifically, the compound having the structure represented by Chemical Formula 1 has excellent hydrolytic decomposability at a high temperature of 45 ° C or higher and decomposes the lithium salt into HF, It is preferable to control the side reaction of the electrolyte such as formation of CO x by decomposition of EC in the non-aqueous organic solvent.

(2)

(3)

[Chemical Formula 4]

In Formula 2-4, wherein R ₁ to R _4, R _{6 ,} R ₈ is alkylene having 1 to 20 carbon atoms and R ₅ is hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, and an arylalkyl group having 6 to 30 carbon atoms Lt; / RTI >

For example, in Formula 2-4, wherein R ₁ to R _4, R _{6 ,} R ₈ is alkylene having 1 to 20 carbon atoms, preferably 3 to 15 alkylene, more preferably 3 to 10 alkylene.

As specific examples, the compound having the structure represented by the formula (1) may be 2-cyano-N, N-bis (cyanomethyl) acetamide, 2-cyano- Acetamide, and 3-cyano-N- (2-cyanoethyl) -N-3-dimethylpropanamide.

The materials included in the above types can effectively control the side reaction of the electrolyte such as decomposition of the lithium salt into HF or formation of COx by decomposition of EC in a non-aqueous organic solvent. For example, Structure, it is preferable to stabilize the electrolytic solution and to inhibit the generation of HF through interaction between acetamide and PF5. In addition, when a high voltage is charged, a large amount of lithium escapes from the anode. Therefore, there is a problem that the charge balance is broken at the anode. The nitrile group included in the formula 1 (specifically, the formulas 2 to 4) plays a role of adjusting the charge balance of the anode Can be performed.

For example, when maintained at a high temperature for a certain time, the lithium salt of conventional LiPF ₆ decomposes according to the following reaction formulas 1 and 2 to generate HF.

[Reaction Scheme 1]

LiPF ₆ → LiF + PF ₅

[Reaction Scheme 2]

PF ₅ + H ₂ O - > 2HF + OPF ₃

Due to the HF generated by the decomposition of the lithium salt as described above, elution of the metal contained in the cathode active material and precipitation of metal ions on the surface of the anode continue to occur, and the electrode cycle may be degraded due to the increase of the potential. The amide compound containing an alkyl group inhibits the decomposition reaction of PF _{5 due to} its hydrolysis characteristics before the reaction according to the reaction formula 2, thereby enhancing the high-temperature stability of the lithium salt contained in the electrolyte solution and suppressing the reduction of the discharge capacity of the secondary battery .

The amide compound containing the cyanoalkyl group can be prepared by various known techniques.

The nonaqueous electrolyte of the present invention may contain 0.1 to 10 parts by weight, preferably 0.3 to 7 parts by weight, of the amide compound containing the cyanoalkyl group based on 100 parts by weight of the non-aqueous electrolyte of the lithium salt and the nonaqueous organic solvent. , And more preferably 0.5 to 5 parts by weight. Within the above range, the decomposition reaction of PF ₅ can be suppressed to increase the stability of the electrolytic solution. In particular, high voltage and resistance performance can be improved, and cycle characteristics and film characteristics can be improved.

The lithium salt which can be included in the non-aqueous liquid electrolyte of the present invention is LiPF ₆ as an _{example, LiClO 4, LiAsF 6, LiSbF} 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 _{SO 3) 2, LiN (C} 2 F 5 SO 2) 2, LiN (CF 3 SO 2) 2, LiN (CaF 2a + 1 SO 2) (C b F 2b + 1 SO 2) ( However, a and b Is a natural number), LiCl, LiI and LiB (C ₂ O ₄ ) ₂ , and preferably LiPF ₆ can be used.

For example, the lithium salt may be contained in the non-aqueous electrolyte at a concentration of 0.6M to 2.0M or 0.7M to 1.6M, and the electrolytic solution has a high conductivity in the range, and the viscosity of the electrolyte is low, There is an effect of excellent mobility.

For example, the non-aqueous electrolyte may have a lithium ion conductivity of 0.3 S / m or 0.3 to 10 S / m at 25 ° C, and the cycle life characteristics of the lithium secondary battery may be further improved within the above range.

The nonaqueous organic solvent that can be included in the nonaqueous electrolyte solution is not limited as long as it can minimize decomposition due to an oxidation reaction during charging and discharging of the battery and can exhibit desired properties together with additives. For example, Based compound, a propionate-based compound, and the like. These may be used alone, or two or more of them may be used in combination.

Examples of the organic solvent of the carbonate compound in the non-aqueous organic solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate And may be any one selected from the group consisting of ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) and vinylene carbonate (VC) or a mixture of two or more thereof.

Among the carbonate-based solvents, more preferred is a carbonate-based organic solvent having a high ionic conductivity capable of improving the charge-discharge performance of the battery, and a carbonate having a viscosity low enough to suitably control the viscosity of the organic solvent having the high- Based organic solvent may be mixed and used.

Specifically, an organic solvent having a high dielectric constant selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and an organic solvent having a low viscosity selected from the group consisting of ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, Can be mixed and used.

Preferably, the organic solvent having a high dielectric constant and the organic solvent having a low viscosity are mixed in a volume ratio of 2: 8 to 8: 2, and more specifically, ethylene carbonate or propylene carbonate; Ethyl methyl carbonate; And dimethyl carbonate or diethyl carbonate in a volume ratio of 5: 1: 1 to 2: 5: 3, for example, 3: 5: 2.

The carbonate compound may be, for example, 10 to 30% by weight or 15 to 25% by weight of ethylene carbonate (EC), 0 to 30% by weight or 1 to 10% by weight of propylene carbonate (PC) To 50% by weight, or 25 to 40% by weight, and diethyl carbonate (DEC) in an amount of 10 to 40% by weight, or 20 to 30% by weight.

The electrolytic solution further includes an additive (hereinafter referred to as "other additive") which can be generally used for electrolytic solution for the purpose of improving lifetime characteristics of the battery, suppressing reduction in battery capacity, improving discharge capacity of the battery, etc. can do.

The other additives may be, for example, metal fluoride. When the metal fluoride is further included as the other additives, the influence of acid generated in the vicinity of the cathode active material is reduced, and the effect of the cathode active material and the electrolyte The reaction can be suppressed and the phenomenon that the capacity of the battery is sharply reduced can be improved.

The metal fluoride is specifically, LiF, RbF, TiF, AgF , AgF 2, BaF 2, CaF 2, CdF 2, FeF 2, HgF 2, Hg 2 F 2, MnF 2, NiF 2, PbF 2, SnF 2 _{, SrF 2, XeF 2, ZnF} 2, AlF 3, BF 3, BiF 3, CeF 3, CrF 3, DyF 3, EuF 3, GaF 3, GdF 3, FeF 3, HoF 3, InF 3, LaF 3, LuF ₃ , MnF ₃ , NdF ₃ , PrF ₃ , SbF ₃ , ScF ₃ , SmF ₃ , TbF ₃ , TiF ₃ , TmF ₃ , YF ₃ , YbF ₃ , TIF ₃ , CeF ₄ , GeF ₄ , HfF ₄ , SiF ₄ , _{SnF 4, TiF 4, VF 4} , ZrF 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6, WF 6, CoF 2, CoF 3, CrF 2, CsF, ErF 3, PF ₃ , PbF ₃ , PbF ₄ , ThF ₄ , TaF ₅ and SeF ₆ .

Examples of the other additives include glutaronitrile (GN), succinonitrile (SN), adiponitrile (AN), 4-tolunitrile, 1, 3,6-hexanetricarbonitrile, 3,3'-thiodipropionitrile (TPN), difluoroethylenecarbonate, fluoro (3,3'-thiodipropionitrile) (Malonato oxalato) borate, LiMOB), LiPF ₂ C ₄ O ₈ , LiSO ₃ CF ₃ , LiPF ₄ (also referred to as LiPF ₂ ), and the like. _{C2O4), C 2 O (LiP} 4) 3, LiC (SO 2 CF 3) 3, LiBF 3 (CF 3 CF 2), LiPF 3 (CF 3 CF 2) 3, Li 2 B 12 F 12, biphenyl ( biphenayl, cyclohexyl benzene, 4-fluorotoluene, ethylene sulfate anhydride, tris (trimethylsilyl) borane Lithium bis (oxalato) borate, lithium difluoro (oxalate) borate (Oxalato), borate, tris (methylsilyl) borate, succinic anhydride ) Borate, LiDFOB, ethylene sulfate (ESA), Fluoro Ethylene Carbonate (FEC), Vinyl Ethylene Carbonate (VEC), Vinylene Carbonate (VC) 1,3-propane sultone (PRS), 1,3-propane sultone (PS), lithium tetrafluoroborate (LiBF4), lithium bis LiFSI), Lithium Bis (trifluoromethane) sulfonamide, LiTFSi, maleic anhydride (MA), 1,1,1,2-tetrafluoroborate , 2,2,3,3-hexafluoropropane-1,3-disulfonamide lithium (1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimi de lithium salt, LiHFP, perfluorohexane-1,6-dinitrile, 3-fluoro-1,3-propansultone, Butyrolactone (GBL), Fluorized? -Butyrolactone (F-GBL), 2-methyl-1,3-butadiene, , And 2-methyl-1,5-hexadiene.

The electrolyte solution may contain 0.1 to 10 parts by weight, or 0.2 to 5 parts by weight, based on 100 parts by weight of the total amount of the electrolyte solution, and the cycle life characteristics of the lithium secondary battery may be further improved have.

The electrolyte according to the present invention having the above composition has excellent stability in a temperature range of -20 ° C to 60 ° C and can be electrochemically stable even at a voltage of about 4V range so that when the battery is applied to a lithium secondary battery, Can be extended.

According to the lithium secondary battery using the nonaqueous electrolyte, a nonaqueous electrolyte secondary battery having a high capacity and a small amount of gas generated inside the battery as compared with the prior art and having high safety and reliability can be obtained. In addition, since the structure of the battery itself is the same as a general non-aqueous electrolyte secondary battery, it is easy to manufacture and is advantageous in mass production.

A lithium secondary battery according to the present invention includes: a positive electrode; cathode; A separator provided between the anode and the cathode; And a nonaqueous electrolytic solution. The non-aqueous electrolyte may include the non-aqueous electrolyte, and the positive electrode and the negative electrode may include a positive electrode active material and a negative electrode active material, respectively.

The anode may be prepared by preparing a composition for forming a cathode active material layer by mixing a cathode active material, a binder and an optional conductive agent, and then applying the composition to a cathode current collector such as an aluminum foil.

As the cathode active material, for example, a conventional NCM cathode active material used in a lithium secondary battery may be used. Specific examples thereof include Li [Ni _x Co _{1-x y} Mn _y ] O ₂ where 0 <x < 0.5). &Lt; / RTI &gt; The variables x and y of the lithium composite metal oxide Li [Ni _x Co _{1-x y} Mn _y ] O ₂ are 0.0001 <x <0.5, 0.0001 <y <0.5, or 0.001 <x <0.3 and 0.001 <y &Lt; 0.3.

As another example of the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used. Among these compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (where 0 <x <1) and LiMl _x M2 _y O ₂ (However, 0≤x≤1, 0≤y≤1, 0≤x + y≤1 , M1 and M2 is any selected from the group consisting of each independently selected from Al, Sr, Mg and La ) Is preferable.

The negative electrode may be prepared by mixing a negative electrode active material, a binder and optionally a conductive agent to prepare a composition for forming a negative electrode active material layer, and then applying the composition to a negative electrode current collector such as a copper foil.

As the negative electrode active material, for example, a compound capable of reversible intercalation and deintercalation of lithium may be used.

Specific examples of the negative electrode active material may include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon. Further, in addition to the carbonaceous material, a compound including a metallic compound capable of alloying with lithium or a metallic compound and a carbonaceous material may be used as the negative electrode active material. For example, it may be graphite.

At least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys may be used as the metal capable of being alloyed with lithium. Further, a metal lithium thin film may be used as the negative electrode active material.

As the negative electrode active material, at least one selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite, lithium metal and lithium-containing alloy may be used in view of high stability.

For example, the battery assembly may be completed by inserting a separator between the positive electrode and the negative electrode, inserting the separator into the cell, injecting and sealing the electrolyte. Here, the lithium secondary battery including the electrolyte, anode, cathode, and separator may be a unit cell having a structure of anode / separator / cathode, a bi-cell having a structure of anode / separator / cathode / separator / anode, The structure of the laminated cell in which the structure of the laminated cell is repeated is obvious.

The lithium secondary battery according to the present invention can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and the electrolytic solution used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin film type. The electrolytic solution according to the embodiment of the present invention is particularly excellent for application to a lithium ion battery, an aluminum laminated battery and a lithium polymer battery.

The lithium secondary battery comprising the electrolytic solution according to the present invention has a lifetime characteristic particularly at a high temperature of 45 占 폚 or higher, for example 45 占 폚 to 60 占 폚, and a high charging voltage (reduction potential) of 4.3 V to 5.0 V And can be used in a portable device such as a mobile phone, a notebook computer, a digital camera, a camcorder, an electric vehicle field such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (plug-in HEV, PHEV) And may be useful for medium to large energy storage systems.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

[Example]

The following examples and experimental examples further illustrate the present invention, but the present invention is not limited thereto.

Example 1

Preparation of electrolyte additives

As the amide compound containing a cyanoalkyl group,

 [Chemical Formula 4]

(Wherein R &lt; _{6 &} And R &lt; ₈ &gt; is methylene).

Preparation of electrolytic solution

1.15 M of LiPF ₆ was mixed with a mixed solution (volume ratio: EC / EMC / DEC = 3/5/2) of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DEC) 1.0 parts by weight of the electrolyte additive was added as a non-aqueous electrolyte to prepare a non-aqueous electrolyte.

Manufacture of lithium secondary battery

96% by weight of an NCM-based positive electrode active material containing Li [Ni _x Co _1-xy Mn _y ] O ₂ where 0 <x <0.5 and 0 <y <0.5, 2% by weight of carbon black as a conductive agent, 2% by weight of vinylidene fluoride (PVdF) was added to the solvent N-methyl-2-pyrrolidone (NMP) to prepare a cathode active material slurry. The positive electrode active material slurry was applied to an aluminum foil as a current collector having a thickness of about 20 탆 and dried to prepare a positive electrode, followed by preparing a positive electrode through a roll press process.

The negative electrode mixture slurry was prepared by adding graphite as an anode active material, PVdF as a binder and carbon black as a conductive agent to solvent NMP at 96 wt%, 3 wt% and 1 wt%, respectively. The negative electrode mixture slurry was applied to a copper (Cu) thin film as a negative electrode current collector having a thickness of 10 mu m and dried to prepare a negative electrode. Then, a negative electrode was prepared through a roll press process.

A lithium rechargeable battery for evaluation was prepared by using a prepared positive electrode and negative electrode, a nonaqueous electrolyte, and a separator of a microporous polypropylene film having a thickness of 20 mu m.

Example 2

As the electrolyte additive,

(3)

(Wherein R &lt; ₃ &gt; is methylene, R &lt; ₄ &gt; _and R &lt; ₅ &gt; is ethylene) was prepared in the same manner as in Example 1 to prepare a lithium secondary battery.

Example 3

As the electrolyte additive,

(2)

Except that 1 part by weight of a compound represented by the following formula (1) was replaced by 1 part by weight of a compound represented by the following formula (R ₁ is propylene and R ₂ is ethylene).

Comparative Example 1

A lithium secondary battery was produced in the same manner as in Example 1 except that no electrolyte additive was added.

Reference Example 1

A lithium secondary battery was prepared in the same manner as in Example 3, except that 0.01 part by weight of the compound of Formula 2 was used as the electrolyte additive .

Reference Example 2

A lithium secondary battery was prepared in the same manner as in Example 1 except that 12 parts by weight of the compound of Formula 4 was used as the electrolyte additive .

<Battery Evaluation>

The produced lithium secondary battery was allowed to stand at room temperature overnight, and then charged and discharged using a secondary battery charge / discharge tester (Battronix). First, the voltage of the test cell was charged to 1.0V-CCCV-4.45V, 0.04C, and after reaching 4.45V, the cell voltage was kept at 4.45V to reduce the current, It was discharged until CC-3.0V and rested for 10 minutes. The charge / discharge efficiency calculated by the difference (charge / discharge capacity) and the discharge capacity (percentage) is shown in Table 1.

Electrolyte composition 1 cycle discharge capacity 200 cycle discharge capacity efficiency 60 ° C (mAh) (mAh) (%) Example 1 840.7 692.737 82.4% Example 2 841.1 691.384 82.2% Example 3 840.8 698.705 83.1% Comparative Example 1 840.1 345.281 41.1% Reference Example 1 841.3 430.746 51.2% Reference Example 2 840.9 329.633 39.2%

Referring to Table 1, in Examples 1 to 3 containing the amide compound containing the cyanoalkyl group of the present invention when charging / discharging was performed at a high voltage, Comparative Example 1 containing no amide compound containing a cyanoalkyl group , Or an amide compound containing a cyanoalkyl group, but showed an efficiency as high as 1.6 to 2.1 times higher than those of Reference Examples 1 to 2 used in an inappropriate range of content.

<Gas generation test>

The cells prepared in Examples 1, 2, 3, and Comparative Example 1 and Reference Examples 1 and 2 were filled up to 4.45 V under a condition of 455 mA (CC / CV), and left at 60 캜 for 30 days. After 30 days, the battery was again charged to 4.45 V under the condition of 455 mA (CC / CV), and the recovery capacity was measured. The results are shown in Table 2 below.

Electrolyte composition High Temperature Lifetime Efficiency (%) Recovery capacity (%) Thickness change (mm)
After 30 days 45 ° C After 30 days After 30 days Example 1 80.2 82.1% 10.2 Example 2 80.1 81.8 11.1 Example 3 81.2 82.8 10.8 Comparative Example 1 36.4 39.1 121.3 Reference Example 1 45.1 48.2 122.2 Reference Example 2 32.4 35.4 34.5

Referring to Table 2, when the battery was charged / discharged at a high voltage after high-temperature storage, Examples 1 to 3 containing an amide compound containing a cyanoalkyl group in the present invention did not contain an amide compound containing a cyanoalkyl group The high temperature lifetime efficiency, the recovery capacity, and the thickness variation (HF production due to lithium salt decomposition under high temperature, CO ₂ and CO ₃ due to decomposition of EC) in Comparative Example 1 or in Reference Examples 1 and 2 included in an inadequate content range Corresponding to gas gauging measurements as gas thickness variations).

Claims (9)

Non-aqueous organic solvent; Lithium salts; And an amide compound containing a cyanoalkyl group, wherein the amide compound containing a cyanoalkyl group is represented by the following formula (1)
[Chemical Formula 1]

(Wherein R ₁ and R ₃ are alkylene having 1 to 20 carbon atoms and R ₂ is hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, An arylalkyl group having 6 to 30 carbon atoms, and a cyanoalkyl group having 1 to 20 carbon atoms). The method according to claim 1,
The non-aqueous electrolyte according to claim 1, wherein the compound represented by the formula (1) comprises at least one selected from the group consisting of compounds represented by the following formulas (2) to (4)
(2)

(3)

[Chemical Formula 4]

(In the formula 2-4, wherein R ₁ to R _4, R _{6 ,} R ₈ is alkylene having 1 to 20 carbon atoms and R ₅ is hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, and an arylalkyl group having 6 to 30 carbon atoms Lt; / RTI &gt; The method according to claim 1,
The compound having the structure represented by the above-mentioned formula (1) can be obtained by reacting 2-cyano-N, N-bis (cyanomethyl) acetamide, 2-cyano- And 3-cyano-N- (2-cyanoethyl) -N-3-dimethylpropanamide. The method according to claim 1,
Wherein the content of the compound having the structure represented by the formula (1) is 0.1 to 10 parts by weight based on 100 parts by weight of the electrolyte solution of the lithium salt and the non-aqueous organic solvent. The method according to claim 1,
The lithium salt is _{LiPF 6, LiClO 4, LiAsF 6} , LiSbF 6, LiAl0 4, LiAlCl 4, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiN (C 2 F 5 SO 3) 2, LiN (C 2 F _{5 SO 2) 2, LiN (} CF 3 SO 2) 2, LiN (CaF 2a + 1 SO 2) (C b F 2b + 1 SO 2) ( However, a and b are natural numbers), LiCl, LiI, and LiB (C ₂ O ₄ ) _{2. 2. The} non-aqueous electrolyte according to claim 1, The method according to claim 1,
The nonaqueous organic solvent may be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC) EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC). The method according to claim 6,
The non-aqueous organic solvent may include 10 to 30% by weight of ethylene carbonate (EC), 0 to 30% by weight of fluoroethylene carbonate (FEC), 10 to 50% by weight of ethylmethyl carbonate (EMC) DEC) in an amount of 10 to 40% by weight. anode; cathode; A separator; And a nonaqueous electrolytic solution,
Wherein the anode is a manganese spinel-based active material or a lithium metal oxide,
The negative electrode is a carbon-based negative electrode active material selected from the group consisting of crystalline carbon, amorphous carbon, artificial graphite, and natural graphite,
The lithium secondary battery according to any one of claims 1 to 7, wherein the non-aqueous electrolyte is an electrolyte solution. 9. The method of claim 8,
Wherein the lithium secondary battery is a lithium ion secondary battery or a lithium polymer secondary battery.