KR102683062B1 - Nonaqueous electrolytic solution and lithium secondary battery - Google Patents

Abstract

The present invention provides a non-aqueous electrolyte solution containing an amide compound containing a cyanoalkyl group as an electrolyte solution additive, and a lithium secondary battery containing the same. A lithium secondary battery using a non-aqueous electrolyte containing the electrolyte additive of the present invention has excellent cycle life characteristics, can extend the life of the battery, and can provide an effect of increasing discharge capacity by using the electrolyte additive.

Description

Non-aqueous electrolyte and lithium secondary battery {NONAQUEOUS ELECTROLYTIC SOLUTION AND LITHIUM SECONDARY BATTERY}

The present invention relates to a non-aqueous electrolyte solution containing an amide compound containing a cyanoalkyl group as an electrolyte solution additive and a lithium secondary battery containing the same. More specifically, the present invention relates to a cycle by using an amide compound containing a cyanoalkyl group as an electrolyte solution additive. The object of the present invention is to provide a non-aqueous electrolyte that has excellent lifespan characteristics, can extend the life of the battery, and has the effect of increasing discharge capacity, and a lithium secondary battery containing the same.

Lithium secondary batteries enable smooth movement of lithium ions by placing an electrolyte between the anode and cathode, and electricity is generated or consumed through redox reactions due to insertion and detachment from the anode and cathode.

Lithium secondary batteries, which are mainly used as a power source for mobile IT devices such as mobile phones and power tools, are being used for purposes such as automobiles and energy storage as large-capacity technology develops.

With the expansion of such application fields and the increase in demand, better battery performance and stability than those required for existing small batteries are required, and in recent years, battery characteristics such as output characteristics, cycle characteristics, preservation characteristics, and film characteristics have been improved. In order to improve, various studies are being conducted on organic solvents and additives as electrolyte components.

Conventionally, in the case of electrolyte solutions that do not contain electrolyte additives or contain electrolyte additives with poor properties, it was difficult to expect improvement in low-temperature output characteristics due to the formation of a non-uniform SEI film. Moreover, even when electrolyte additives are included, if the input amount is not adjusted to the required amount, the electrolyte additives may cause the anode surface to decompose during a high temperature reaction or cause an oxidation reaction in the electrolyte, ultimately increasing the irreversible capacity of the secondary battery and output characteristics. There was a problem with this deterioration.

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, the purpose of the present invention is to provide an electrolyte solution that has excellent cycle life characteristics, can extend the life of the battery, and has the effect of increasing discharge capacity, and a lithium secondary battery containing the same. do.

The above and other objects of the present invention can all be achieved by the present invention described below.

In order to achieve the above object, the present invention includes a non-aqueous organic solvent; lithium salt; and an amide compound containing a cyanoalkyl group; wherein the amide compound containing the cyanoalkyl group has the following formula (1)

[Formula 1]

(In Formula 1, 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, It is any one selected from the group consisting of an arylalkyl group having 6 to 30 carbon atoms and a cyanoalkyl group having 1 to 20 carbon atoms).

According to this non-aqueous electrolyte, it has high capacity, high initial charge and discharge efficiency, and gas generation inside the battery is safer and more reliable than conventional non-aqueous electrolyte secondary batteries.

In addition, the present invention is an anode; cathode; separator; and non-aqueous electrolyte,

The positive electrode is a manganese spinel-based active material or lithium metal oxide, the negative electrode is a carbon-based negative active material selected from the group consisting of crystalline carbon, amorphous carbon, artificial graphite, and natural graphite, and the non-aqueous electrolyte is the electrolyte solution described above. Provides a lithium secondary battery that

By using a lithium secondary battery using the above-described electrolyte, it has high capacity and excellent initial charge/discharge efficiency and cycle characteristics, and can also reduce gas generation inside the battery, providing a lithium secondary battery with high safety and reliability. You can.

According to the present invention, an electrolyte solution that has excellent room temperature and high temperature lifespan characteristics, can extend the life of a battery, and has the effect of increasing discharge capacity is provided. Therefore, in the case of a lithium secondary battery containing a positive electrode manufactured using this, there is an advantage in that it is possible to secure excellent battery life characteristics while increasing capacity.

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

The non-aqueous electrolyte of the present invention includes a non-aqueous organic solvent; lithium salt; And amide compounds containing a cyanoalkyl group;

The amide compound containing the cyanoalkyl group has the following formula (1)

[Formula 1]

(In Formula 1, 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, It is characterized as being a compound having a structure represented by any one selected from the group consisting of an arylalkyl group having 6 to 30 carbon atoms and a cyanoalkyl group having 1 to 20 carbon atoms.

When the amide compound containing the cyanoalkyl group is included as an additive in a non-aqueous electrolyte to form a lithium secondary battery, the lithium salt is decomposed into HF when stored at high temperature, or COx is generated by decomposition of EC, for example, in a non-aqueous organic solvent. By suppressing electrolyte side reactions such as these, it is possible to provide a secondary battery with higher capacity than before and less gas generation inside the battery, with high safety and reliability.

Specifically, the compound having the structure represented by Formula 1 above has excellent hydrolyzability at a high temperature of 45°C or higher, and the lithium salt decomposes into HF or It is desirable because it can effectively control electrolyte side reactions, such as the generation of COx from the decomposition of EC, for example, among non-aqueous organic solvents.

[Formula 2]

[Formula 3]

[Formula 4]

In Formulas 2 to 4, R ₁ to R _4, R ₆ to 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. It is one selected from .

For example, in Formulas 2 to 4, R ₁ to R _4, R ₆ to R ₈ may be alkylene having 1 to 20 carbon atoms, preferably alkylene having 3 to 15 carbon atoms, and more preferably alkylene having 3 to 10 carbon atoms.

As a specific example, the compound having the structure represented by Formula 1 is 2-cyano-N,N-bis(cyanomethyl)acetamide, 2-cyano-N-(2-cyanoethyl)-N-ethyl It may be one or more selected from the group consisting of acetamide, and 3-cyano-N-(2-cyanoethyl)-N-3-dimethylpropane amide.

Substances included in the above types can effectively control electrolyte side reactions such as the decomposition of lithium salts into HF or the generation of COx by decomposition of EC in non-aqueous organic solvents, for example, represented by Formula 1 above. Among the compounds having the structure, it is preferable because it can stabilize the electrolyte solution through the interaction between acetamide and PF5 and suppress the formation of HF. In addition, during high-voltage charging, a lot of lithium escapes from the anode, causing a problem of the charge balance being broken at the anode. This is because the nitrile group contained in Formula 1 (specifically Formulas 2 to 4) plays a role in balancing the charge of the anode. It can be done.

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

[Scheme 1]

LiPF ₆ → LiF + PF ₅

[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, the elution of the metal contained in the positive electrode active material and the precipitation of metal ions on the positive electrode surface continue to occur, which may cause the electrode cycle to deteriorate due to an increase in electric potential. Amide compounds containing alkyl groups have the property of being hydrolyzed before the reaction according to Scheme 2 occurs, thereby suppressing the decomposition reaction of PF ₅ , thereby increasing the high-temperature stability of the lithium salt contained in the electrolyte solution and suppressing the decrease in discharge capacity of secondary batteries. You can do it.

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

The non-aqueous electrolyte of the present invention may contain 0.1 to 10 parts by weight of the amide compound containing the cyanoalkyl group, preferably 0.3 to 7 parts by weight, based on 100 parts by weight of the non-aqueous electrolyte of lithium salt and non-aqueous organic solvent. It can be done, and more preferably, it can be included in 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 electrolyte solution. In particular, high voltage and resistance performance can be improved, and cycle characteristics and film characteristics can be improved.

Lithium salts that can be included in the non-aqueous electrolyte of the present invention include, for example, 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 is a natural number), LiCl, LiI and LiB(C ₂ O ₄ ) ₂ may be used, and LiPF ₆ is preferably used.

For example, the lithium salt may be included in the non-aqueous electrolyte at a concentration of 0.6M to 2.0M or 0.7M to 1.6M. Within this range, the conductivity of the electrolyte is high, so electrolyte performance is excellent, and the viscosity of the electrolyte is low, so lithium ions It has excellent mobility.

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

In addition, the non-aqueous organic solvent that can be included in the non-aqueous electrolyte is not limited as long as it can minimize decomposition due to oxidation reactions during the charging and discharging process of the battery and can exhibit the desired properties together with additives, for example, carbonate. It may be a type compound, a propionate type compound, etc. These may be used individually, or two or more types may be used in combination.

Among the non-aqueous organic solvents, organic solvents for carbonate-based compounds include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), and methyl. It 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 preferably a carbonate-based organic solvent with a high dielectric constant that can increase the charging and discharging performance of the battery, and a carbonate-based organic solvent with a low viscosity that can appropriately control the viscosity of the high dielectric constant organic solvent. It may be desirable to use a mixture of organic solvents.

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

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

The carbonate-based compound is, 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), and 10 to 10% by weight of ethylmethyl carbonate (EMC). It can be used as a mixture of 50 to 50% by weight, or 25 to 40% by weight, and 10 to 40% by weight, or 20 to 30% by weight, of diethyl carbonate (DEC).

In addition to the electrolyte components, the electrolyte solution further includes additives (hereinafter referred to as 'other additives') that can be generally used in electrolyte solutions for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. can do.

The other additive may be, for example, metal fluoride, and when the metal fluoride is further included as the other additive, the influence of the acid generated around the positive electrode active material is reduced and the influence of the positive electrode active material and the electrolyte solution is reduced. By suppressing the reaction, the phenomenon of rapid decrease in battery capacity 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 , ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 , It may be one or more selected from the group consisting of PF ₃ , PbF ₃ , PbF ₄ , ThF ₄ , TaF ₅ and SeF ₆ .

The other additives include, for example, glutanonitrile (GN), succinonitrile (SN), adiponitrile (AN), 4-tolunitrile (4-tolunitrile), 1, 3,6-hexanetricarbonitrile (1,3,6-hexanetricarbonitrile), 3,3'-thiodipropionitrile (TPN), difluoroethylenecarbonate, fluoro Dimethylcarbonate (fluorodimethylcarbonate), fluoroethylmethylcarbonate, Lithium (malonato oxalato) borate (LiMOB), LiPF ₂ C ₄ O ₈ , LiSO ₃ CF ₃ , LiPF ₄ ( C2O4), LiP(C ₂ O 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(methylsilyl)borate, succinic anhydride ( succinic anhydride (SA), Lithium Bis(oxalto)borate (LiBOB), Lithium DiFluro(Oxalato) Borate (LiDFOB), ethylene sulfate, ESA), Fluoro Ethylene Carbonate (FEC), Vinyl Ethylene Carbonate (VEC), Vinylene Carbonate (VC), 1,3-Propene sultone , PRS), 1,3-Propane Sultane (PS), Lithium Tetrafluoroborate (LiBF4), Lithium bis(fluorosulfonyl)imide , LiFSI), Lithium Bis(trifluoromethane)sulfonamide, LiTFSi), Maleic anhydride (MA), 1,1,2,2,3,3-hexafluoro Lithium propane-1,3-disulfonamide (1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium salt, LiHFP), Perfluorohexane-1,6-dinitrile (PFDN) ), 3-Fluoro-1,3-propansulton (FPS), γ-butyrolactone (GBL), Fluorized γ-butyrolactone, F-GBL), 2-methyl-1,3-butadiene, and 2-methyl-1,5-hexadiene (2-Methyl-1,5- It may be one or more types selected from the group consisting of hexadiene).

For example, the electrolyte may include the other additives in an amount of 0.1 to 10 parts by weight, or 0.2 to 5 parts by weight based on a total of 100 parts by weight of the electrolyte, and within this range, the cycle life characteristics of the lithium secondary battery can be further improved. there is.

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

According to the lithium secondary battery using the above-mentioned non-aqueous electrolyte, it has a higher capacity than the conventional battery and generates less gas inside the battery, resulting in a non-aqueous electrolyte secondary battery with high safety and reliability. Additionally, the structure of the battery itself is the same as that of a typical non-aqueous electrolyte secondary battery, making it easy to manufacture and advantageous for mass production.

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

The positive electrode can be manufactured, for example, by mixing a positive active material, a binder, and optionally a conductive agent to prepare a composition for forming a positive active material layer, and then applying the composition to a positive current collector such as aluminum foil.

For example, the positive electrode active material may be a typical NCM positive electrode active material used in lithium secondary batteries, and as a specific example, it has the chemical formula Li[Ni _x Co _1-xy Mn _y ]O ₂ (where 0<x<0.5, 0<y< 0.5), but is not limited thereto. The variables _{x and y} of the chemical formula Li[ _Ni It may be <0.3.

As another example, the positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound). Among the above compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (however, 0<x<1), and _{LiMl ​ ​} ), at least one selected from the group consisting of is preferable.

The negative electrode can be manufactured, for example, 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 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 be carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon. Additionally, in addition to the carbonaceous material, a metallic compound capable of alloying with lithium or a composite containing a metallic compound and a carbonaceous material can also be used as a negative electrode active material. For example, it may be graphite.

As a metal capable of alloying with lithium, for example, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy may be used. Additionally, a thin film of metallic lithium may be used as the negative electrode active material.

The anode active material may be any one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite, lithium metal, and alloy containing lithium in terms of high stability.

For example, the battery assembly can be completed by placing a separator between the above-described anode and the cathode, inserting it into the cell, then injecting an electrolyte and sealing it. At this time, the lithium secondary battery containing the above-mentioned electrolyte, positive electrode, negative electrode, and separator is, for example, a unit cell having a positive electrode/separator/negative electrode structure, a bicell, or a unit cell having a positive electrode/separator/negative electrode/separator/positive electrode structure. It is a self-evident fact that the structure of can be formed into a structure of repeating stacked cells.

Lithium secondary batteries according to the present disclosure can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin, pouch, etc. depending on their shape. It can be classified into bulk type and thin film type depending on size. The electrolyte solution according to the embodiment of the present disclosure is particularly excellent for application to lithium ion batteries, aluminum laminated batteries, and lithium polymer batteries.

The lithium secondary battery containing the electrolyte according to the present disclosure has life characteristics, especially at high temperatures of 45°C or higher, for example, 45°C to 60°C, and at a high charging voltage (reduction potential) of 4.3 V or higher, for example, 4.3 V to 6.0 V. It can be improved in the field of portable devices such as mobile phones, laptop computers, digital cameras, and camcorders, and electric vehicles such as hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (plug-in HEV, PHEV), And it can be useful in medium to large energy storage systems.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is clear to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the attached patent claims.

[Example]

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

Example 1

Preparation of electrolyte additives

An amide compound containing a cyanoalkyl group, having the following formula 4:

[Formula 4]

(R ₆ to A compound having a structure represented by (R ₈ is methylene) was prepared.

Preparation of electrolyte solution

1.15M LiPF ₆ was mixed with a mixed solution of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DEC) (volume ratio: EC/EMC/DEC = 3/5/2), then 100 wt. A non-aqueous electrolyte solution was prepared by adding 1.0 parts by weight of the electrolyte additive.

Manufacturing of lithium secondary batteries

₉₆ % by weight _of NCM-based positive _electrode active material containing Li[ _Ni A positive electrode active material slurry was prepared by adding 2% by weight of vinylidene fluoride (PVdF) to the solvent N-methyl-2-pyrrolidone (NMP). The positive electrode active material slurry was applied and dried on an aluminum thin film as a current collector with a thickness of about 20㎛ to manufacture a positive electrode, and then the positive electrode was prepared through a roll press process.

In addition, graphite as a negative electrode active material, PVdF as a binder, and carbon black as a conductive agent were added at 96% by weight, 3% by weight, and 1% by weight, respectively, to the solvent NMP to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied and dried on a copper (Cu) thin film, which is a negative electrode current collector, with a thickness of 10 μm, and the negative electrode was prepared through a roll press process.

A lithium secondary battery for evaluation was manufactured using the prepared positive and negative electrodes, a non-aqueous electrolyte, and a separator of a microporous polypropylene film with a thickness of 20 μm.

Example 2

As the electrolyte additive, the following formula 3

[Formula 3]

(The R ₃ is methylene, A lithium secondary battery was manufactured in the same manner as in Example 1, except that it was replaced with 1 part by weight of a compound represented by (R _{4 and} R ₅ are ethylene).

Example 3

As the electrolyte additive, the following formula 2

[Formula 2]

A lithium secondary battery was manufactured in the same manner as in Example 1, except that it was replaced with 1 part by weight of a compound represented by (R ₁ is propylene and R ₂ is ethylene).

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as Example 1, except that electrolyte additives were not added.

Reference example 1

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

Reference example 2

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

<Battery evaluation>

The manufactured lithium secondary battery was left at room temperature overnight, and then charged and discharged using a secondary battery charge and discharge test device (manufactured by Battronix). First, the voltage of the test cell was charged to 1.0V-CCCV-4.45V, 0.04C, and after it reached 4.45V, it was charged by reducing the current to keep the cell voltage at 4.45V, and after a 10-minute rest, 1.0C- It was discharged until CC-3.0V and rested for 10 minutes. The above operation was repeated for 200 cycles, and the charge/discharge efficiency calculated as the difference (percentage) between charge/discharge capacity and discharge capacity is shown in Table 1.

Electrolyte composition 1 cycle discharge capacity 200cycle discharge capacity efficiency 60℃ (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, when charged/discharged at high voltage, Examples 1 to 3 containing the amide compound containing a cyanoalkyl group of the present invention are compared to Comparative Example 1 which does not contain an amide compound containing a cyanoalkyl group. , or an amide compound containing a cyanoalkyl group, but showed an efficiency that was 1.6 to 2.1 times higher than Reference Examples 1 to 2, which were used in an inappropriate content range.

<Gas generation test>

The batteries manufactured in Examples 1, 2, and 3, Comparative Examples 1, and Reference Examples 1 and 2 were charged to 4.45 V at 455 mA (CC/CV) and then left at 60°C for 30 days. After 30 days, the left battery was recharged to 4.45 V under 455 mA (CC/CV) conditions and the recovery capacity was measured. The results are shown in Table 2 below.

Electrolyte composition High temperature lifespan efficiency (%) Recovery capacity (%) Thickness change (mm)
After 30 days 45℃ 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 stored at high temperature and then charged/discharged at high voltage, Examples 1 to 3, which contain an amide compound containing a cyanoalkyl group in the present invention, do not contain an amide compound containing a cyanoalkyl group. Compared to Comparative Example 1 or Reference Examples 1 to 2 included in an inappropriate content range, high temperature life efficiency, recovery capacity, and thickness change (HF generation due to lithium salt decomposition at high temperature, CO ₂ and CO ₃ due to decomposition of EC) All of them provided significantly improved results in terms of thickness change due to gas (corresponding to the gas increase amount measurement).

Claims (9)

Non-aqueous organic solvent; lithium salt; and an amide compound containing a cyanoalkyl group; wherein the amide compound containing the cyanoalkyl group has the following formula (1)
[Formula 1]

(In Formula 1, R ₁ and R ₃ are alkylene having 1 to 5 carbon atoms, and R ₂ is hydrogen, an alkyl group having 1 to 5 carbon atoms, and a cyanoalkyl group having 1 to 5 carbon atoms. ) A non-aqueous electrolyte, characterized in that it is a compound having a structure represented by ). delete According to paragraph 1,
Compounds having the structure represented by Formula 1 include 2-cyano-N,N-bis(cyanomethyl)acetamide, 2-cyano-N-(2-cyanoethyl)-N-ethylacetamide, and A non-aqueous electrolyte comprising at least one selected from 3-cyano-N-(2-cyanoethyl)-N-3-dimethyl propanamide. According to paragraph 1,
A non-aqueous electrolyte solution, wherein the content of the compound having the structure represented by Formula 1 is 0.1 to 10 parts by weight based on 100 parts by weight of the total weight of the lithium salt and the non-aqueous organic solvent. According to paragraph 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 ) (where a and b are natural numbers), LiCl, LiI and LiB (C ₂ O ₄ ) A non-aqueous electrolyte comprising at least one selected from the group consisting of ₂ . According to paragraph 1,
The non-aqueous organic solvent includes dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC). According to clause 6,
The non-aqueous organic solvent is 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), and diethyl carbonate ( A non-aqueous electrolyte comprising 10 to 40% by weight of DEC). anode; cathode; separator; and non-aqueous electrolyte,
The positive electrode is a manganese spinel-based active material or lithium metal oxide,
The negative electrode is a carbon-based negative active material selected from the group consisting of crystalline carbon, amorphous carbon, artificial graphite, and natural graphite,
A lithium secondary battery, wherein the non-aqueous electrolyte is the non-aqueous electrolyte of any one of claims 1 and 3 to 7. According to clause 8,
A lithium secondary battery, characterized in that the lithium secondary battery is a lithium ion secondary battery or a lithium polymer secondary battery.