KR20180050781A - Nonaqueous electrolytic solution and lithium secondary battery - Google Patents

Abstract

The present invention provides a non-aqueous electrolytic solution, which comprises a non-aqueous solvent, a lithium salt, an electrolyte additive, a phosphorus compound containing at least three allyl groups, and an organic fluorine compound containing nitrogen or sulfur, and also provides a lithium secondary battery comprising the same. The lithium secondary battery using the non-aqueous electrolyte of the present invention has excellent cycle life characteristics and storage characteristics, and can suppress the decomposition of the electrolyte solution and extend the life of the battery as an increase rate of the internal resistance and the amount of gas generation are reduced when left at a high temperature.

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 and a lithium secondary battery, and more particularly to a nonaqueous electrolyte and a lithium secondary battery comprising a nonaqueous solvent, a lithium salt, an electrolyte additive, a phosphorus compound containing three or more allyl groups, The present invention provides a nonaqueous electrolyte solution and a lithium secondary battery including the nonaqueous electrolyte solution that can improve the high temperature lifetime characteristics and recovery capacity by inhibiting the decomposition of electrolyte solution and reducing the internal resistance increase rate by applying the electrolyte solution to the lithium secondary battery.

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. In addition, 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 during the high temperature reaction due to the electrolyte additive, thereby ultimately deteriorating the cycle characteristics and storage stability of the secondary battery. There was a problem.

Korean Patent No. 10-1099973

In order to solve the problems of the prior art as described above, the present invention has an excellent cycle property and storage characteristics, has an effect of inhibiting decomposition of electrolyte, has a reduced internal resistance increase rate and gas generation amount at high temperature, And a lithium secondary battery including the nonaqueous electrolyte solution.

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

In order to achieve the above object, the present invention provides a nonaqueous solvent, a lithium salt, an electrolyte additive, a phosphorus compound containing at least three allyl groups, and an organic fluorine compound containing nitrogen or sulfur, And 0.1 to 3% by weight of the organic fluorine compound is contained in the non-aqueous electrolyte.

The present invention also relates to a positive electrode comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material selected from the group consisting of a lithium composite metal oxide and a lithium olivine phosphate, Wherein the nonaqueous electrolyte comprises a nonaqueous solvent, a lithium salt, an electrolyte additive, an electrolyte solution containing at least three allyl groups, and a nonaqueous electrolyte containing at least three allyl groups, wherein the nonaqueous electrolyte is selected from the group consisting of silicon compounds, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite and natural graphite. A phosphorus compound, and an organic fluorine compound containing nitrogen or sulfur.

The nonaqueous electrolyte according to the present invention has an effect of inhibiting the decomposition of electrolytic solution. Therefore, in the case of a lithium secondary battery comprising the nonaqueous electrolyte according to the present invention, high temperature lifetime characteristics and recovery capacity are improved owing to the effect of inhibiting electrolyte decomposition, The resistance increase rate is reduced and the stability and reliability of the battery can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the results of measurement of high temperature (45 ° C.) lifetime characteristics of a lithium secondary battery including non-aqueous electrolytes of Examples and Comparative Examples, respectively.
FIG. 2 is a graph showing the results of evaluating the recovery capacity characteristics of a lithium secondary battery including non-aqueous electrolytes in Examples and Comparative Examples at high temperature (60 ° C.).
Fig. 3 is a graph showing the results of evaluating the internal resistance when the lithium secondary batteries each containing the nonaqueous electrolyte solution of the examples and the comparative examples were allowed to stand at high temperature (60 캜).

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 comprises a nonaqueous solvent, a lithium salt, an electrolyte additive, a phosphorus compound containing at least three allyl groups, and an organic fluorine compound containing nitrogen or sulfur, wherein the nitrogen or sulfur- 0.1 to 3% by weight.

When the phosphorus-containing compound containing three or more allyl groups is included as an additive in a non-aqueous electrolyte to constitute a lithium secondary battery, a uniform SEI film is formed on the surface of the electrode so that a side reaction of the lithium salt or decomposition of EC in the non- A secondary battery in which lifetime characteristics and cycle characteristics are improved as the internal resistance increase rate is reduced by reducing the gas generation amount in the battery can be achieved by suppressing the electrolyte side reaction such as generation of hydrocarbon gas, .

The phosphorus-containing compound having three or more allyl groups may be at least one selected from triallyl phosphate and triallyl phosphite, and a non-aqueous electrolyte containing the same may be used to form a lithium secondary battery. The triallyl phosphate or triallyl phosphite forms an alkyl phosphate or an alkyl phosphite, respectively, so as to inhibit the decomposition of the electrolytic solution. As a result, the internal resistance increase rate decreases and the gas generation amount decreases, .

The non-aqueous electrolyte of the present invention may contain 0.1 to 3% by weight, preferably 0.3 to 2% by weight or 0.3 to 1% by weight, of a phosphorus compound containing three or more allyl groups relative to the total weight of the lithium salt and non- %, More preferably from 0.4 to 0.8% by weight, or from 0.4 to 0.6% by weight. Within this range, there is an advantage that the decomposition effect of the electrolytic solution is suppressed, and the lifetime characteristics, cycle characteristics, and the like of the battery are improved.

The organic fluorine compound containing nitrogen or sulfur adsorbs on the metal surface of the electrode to suppress the side reaction between the electrode and the electrolyte, thereby further improving the stability of the electrolyte. Thus, the cycle characteristics, stability and lifetime of the battery can be improved have.

The non-aqueous electrolyte of the present invention may contain 0.1 to 3% by weight, preferably 0.1 to 2.5% by weight, of the organic fluorine compound containing nitrogen or sulfur based on the total weight of the lithium salt and the nonaqueous solvent , And more preferably 0.2 to 2% by weight. Within this range, the effect of inhibiting the side reaction of the electrolyte can be improved to improve the stability of the electrolyte solution and ultimately improve the cycle characteristics, stability and lifetime of the battery. .

The organic fluorine compound containing nitrogen or sulfur may be, for example, perfluoronitrile compounds, fluorosulton compounds, or a mixture thereof. The non-aqueous electrolyte containing the compound as an additive may be used in combination with lithium In the case of constructing the secondary battery, there is an effect of suppressing the side reaction of the electrolyte, thereby improving the cycle characteristics and stability of the battery.

The perfluoronitrile compound may be a compound represented by the following general formula (1).

[Chemical Formula 1]

(In the above formula (1), n is an integer of 1 to 10.)

Specifically, the perfluoronitrile compound may include perfluorohexane-1,6-dinitrile or perfluorosubcononitrile. The perfluoronitrile compound may be perfluorohexane-1,6-dinitrile or perfluorosubcononitrile.

The perfluoronitrile compound may be contained in an amount of 0.1 to 2% by weight, preferably 0.1 to 1% by weight, more preferably 0.1 to 0.5% by weight or 0.2% by weight based on the total weight of the lithium salt and the non- To 0.4% by weight, and the effect of inhibiting the side reaction of the electrolyte within this range can be further improved.

The fluorosulfone compound may be, for example, a compound represented by the following formula (2).

(2)

Wherein at least one of R 1, R 2, R 3, R 4, R 5 and R 6 is fluorine and the others are hydrogen or a C 1 -C 6 alkyl group, 1 < / RTI > to 2 < RTI ID = 0.0 >

Specifically, the fluorosulfone compound may include 3-fluoro-1,3-propane sultone.

The fluorosulfonic compound may be contained in an amount of 0.1 to 3% by weight, preferably 0.1 to 2% by weight, more preferably 0.5 to 1.5% by weight, based on the total weight of the lithium salt and the non- 0.8 to 1.2% by weight. The effect of suppressing the side reaction of the electrolyte can be further improved within the above range, and ultimately the performance and stability of the battery can be improved.

The nonaqueous electrolytic solution of the present invention can maximize the effect of suppressing the side reaction of the electrolyte by using a combination of the phosphoric compound containing three or more allyl groups and the organic or fluorine compound containing nitrogen or sulfur, When the lithium secondary battery is constructed, the amount of gas generated at the time of leaving at a high temperature is reduced, and the rate of increase of the internal resistance is reduced, and ultimately, the life characteristic of the battery is improved.

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

Among the non-aqueous solvents, examples of the carbonate-based organic solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl ethyl carbonate (MEC), fluoroethylene carbonate (FEC), methyl propyl carbonate (MPC) and ethyl propyl carbonate Or more.

Among the carbonate-based organic solvents, a carbonate-based organic solvent having a high ionic conductivity and a carbonate having a high viscosity capable of appropriately controlling the viscosity of the organic solvent having a high ionic conductivity and capable of increasing the charge- 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.

As a specific example, the carbonate-based organic solvent may include ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), and may contain 10 to 40% by weight or 15 to 35% by weight of ethylene carbonate, 20 To 30% by weight or 22 to 28% by weight; 15 to 45 wt%, 20 to 40 wt%, 25 to 35 wt%, or 27 to 33 wt% diethyl carbonate; 30 to 60% by weight, 35 to 55% by weight, 40 to 50% by weight or 42 to 48% by weight of ethylmethyl carbonate can be mixed and used.

Among the non-aqueous solvents, the propionate-based organic solvent may include, for example, propionate, methyl propionate, and the like, but is not limited thereto.

Examples of the lithium salt that can be included in the non-aqueous electrolyte of the present invention include LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiBF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiClO 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 ) ₂ , and preferably LiPF ₆ can be used. The a and b may be an integer of 1 to 4, for example.

For example, the lithium salt may be contained in the non-aqueous electrolyte at a concentration of 0.5 to 1.5 M (mol / L), preferably at a concentration of 0.7 to 1.3 M, more preferably at a concentration of 0.8 to 1.1 M ≪ / RTI > Within this range, the electrolytic solution has a high conductivity because of its high conductivity, and the viscosity of the electrolytic solution is low, resulting in excellent mobility of lithium ions.

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 electrolyte solution may further include an electrolyte additive which can be generally used for an electrolyte solution for the purpose of improving lifetime characteristics of the battery, suppressing reduction in battery capacity, and improving discharge capacity of the battery, in addition to the components of the electrolyte solution.

Examples of the electrolyte additive include glutaronitrile (GN), succinonitrile (SN), adiponitrile (AN), 4-tolunitrile, 1 , 3,6-hexanetricarbonitrile, 3,3'-thiodipropionitrile (TPN), difluoroethylenecarbonate, fluoro (3,3'-thiodipropionitrile) (Fluoromethyl carbonate), lithium (malonato oxalato) borate, LiMOB), lithium tetra fluoro (oxalato) phosphate (lithium tetra fluoro oxalato phosphate, lithium difluorophosphate, LiP (C2O4) 3, LiC (SO2CF3) 3, LiBF3 (CF3CF2), LiPF3 (CF3CF2) 3, Li2B12F12, biphenayl, cyclohexylbenzene cyclohexyl benzene, 4-fluorotoluene, Tris (methylsilyl) borate, succinic anhydride (SA), lithium bis (oxalto) borate, LiBOB, and the like. Lithium hexafluorophosphate, lithium difluoro (oxalato) borate, LiDFOB, ethylene sulfate (ESA), Fluoro Ethylene Carbonate (FEC), Vinyl Ethylene Carbonate ), Vinylene carbonate (VC), 1,3-propene sultone (PRS), 1,3-propane sultone (PS), lithium bis (Fluorosulfonyl) imide, LiFSI), maleic anhydride (MA), 1,1,2,2,3,3-hexafluoropropane-1,3- (1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide lithium salt, LiHFP), perfluorohexane-1,6-dinitrile (PFDN) Fluoro-1,3-propansultone (FPS), gamma-butyrolactone (GBL), fluoro-gamma-butyrolactone, butyrolactone, F-GBL, 2-methyl-1,3-butadiene and 2-Methyl-1,5-hexadiene. And the like.

Preferably, the non-aqueous electrolyte according to the present invention comprises lithium bis (fluorosulfonyl) imide, lithium tetrafluoro (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, Lithium difluorophosphate, lithium bis (oxaleto) borate, 1,3-propane sultone, 1,3-propanesultone (1,3-propane sultone) 1,3-Propene Sultone, Ethylene Sulfate, Vinylene Carbonate, Vinyl Ethylene Carbonate, and Fluoro Ethylene Carbonate. And by including it, the decomposition reaction of the electrolyte can be more effectively suppressed.

In addition, the electrolyte additive may include metal fluoride. When the metal fluoride is further included as the electrolyte additive, the influence caused by the acid generated in the vicinity of the cathode active material is reduced, It is possible to suppress the reaction between the active material and the electrolytic solution and to improve the capacity of the battery dramatically.

Specifically, the metal fluoride is selected from the group consisting of LiF, RbF, TiF, AgF, AgF2, BaF2, CaF2, CdF2, FeF2, HgF2, Hg2F2, MnF2, NiF2, PbF2, SnF2, SrF2, XeF2, ZnF2, AlF3, BF3, BiF3, The present invention is directed to a method of manufacturing a semiconductor device comprising the steps of: forming a first electrode on a substrate, forming a first electrode on the first electrode, forming a first electrode on the first electrode, forming a first electrode on the first electrode, forming a first electrode on the first electrode, As a result, it is possible to form a single-layer structure of HfF4, SiF4, SnF4, TiF4, VF4, ZrF44, NbF5, SbF5, TaF5, BiF5, MoF6, ReF6, SF6, WF6, CoF2, CoF3, CrF2, CsF, ErF3, PF3, PbF3, PbF4, ThF4, And at least one selected from the group consisting of

The electrolyte additive may include, for example, 0.1 to 10% by weight or 0.2 to 5% by weight based on the total weight of the non-aqueous electrolyte, and the cycle life characteristics of the lithium secondary battery may be further improved within this range.

The electrolytic solution according to the present invention having the above composition has a stable and reliable high non-aqueous electrolyte secondary battery as the decomposition reaction of the electrolyte is suppressed in a wide temperature range of -20 캜 to 60 캜, can do. In addition, since the structure of the battery itself is the same as a general non-aqueous electrolyte secondary battery, it is advantageous in that 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.

The cathode active material may be, for example, a conventional lithium composite metal oxide and lithium olivine phosphate used in a lithium secondary battery. Preferably, the cathode active material includes at least one metal selected from the group consisting of cobalt, manganese, nickel and iron And more preferably, NCM (lithium nickel cobalt manganese oxide) can be used.

As a specific example, the cathode active material may be a lithium composite metal oxide in the form of Li [Ni _x Co _{1-x y} Mn _y ] O ₂ (where 0 <x <0.5, 0 <y <0.5). 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.

In addition, the lithium olivine-type phosphate among the positive electrode active material for example, iron, cobalt, may be desirable to include one or more selected from nickel and manganese, and the like Specifically, LiFePO _4, LiCoPO ₄ and LiMnPO ₄ . Also, a compound in which a part of the metal of the lithium olivine phosphate is substituted with another metal may be possible.

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.

The negative electrode active material may include at least one selected from the group consisting of tin, a tin compound, silicon, a silicon compound, lithium titanate, crystalline carbon, amorphous carbon, artificial graphite and natural graphite.

In the present description, the tin compound or the silicon compound is a compound in which tin or silicon is combined with at least one other chemical element, respectively.

Further, in addition to the carbonaceous material including crystalline carbon, amorphous carbon, graphite and the like, 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, a battery assembly may be completed by inserting a separator between the positive electrode and the negative electrode, inserting the separator into the cell, and injecting and sealing the non-aqueous electrolyte. The lithium secondary battery including the non-aqueous electrolyte, the positive electrode, the negative electrode, and the separator may include a unit cell having a positive electrode / separator / negative electrode structure, a bi-cell having a positive electrode / separator / negative electrode / separator / It is a matter of fact that the structure of the laminated cell in which the structure of the cell is repeated can be formed.

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 non-aqueous electrolyte 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 including the non-aqueous electrolyte according to the present invention can improve lifetime characteristics particularly at a high temperature of 45 占 폚 or higher, for example, 45 占 폚 to 60 占 폚, and can be used for portable devices such as mobile phones, notebook computers, digital cameras, , A hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (HEV, PHEV), and a medium to large-sized energy storage system.

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  One

Non-aqueous electrolyte  Produce

Was added to a mixed solution (volume ratio: EC / EMC / DEC = 3/5/2) of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DEC) so that LiPF6 _was 1.0 M, 1.0 part by weight of LiTFOP (lithium tetrafluoro (oxalato) phosphate), 0.5 part by weight of triallyl phosphate represented by the following formula (a), 10 parts by weight of perfluorohexane-1,6-dinitrile 0.3 part by weight were added to prepare a nonaqueous electrolytic solution.

(A)

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.

An Al-pouch-type lithium secondary battery was prepared using the prepared anode and cathode and the previously prepared electrolyte solution.

Example  2

The procedure of Example 1 was repeated except that 0.3 part by weight of perfluorohexane-1,6-dinitrile was replaced by 0.5 part by weight of perfluorocycononitrile in the preparation of the non-aqueous electrolyte of Example 1, .

Example  3

In the same manner as in Example 1 except that 0.3 part by weight of perfluorohexane-1,6-dinitrile was replaced by 0.5 part by weight of 3-fluoro-1,3-propanesultone in the preparation of the non-aqueous electrolyte of Example 1 Thereby preparing a secondary battery.

Example  4

A secondary battery was manufactured in the same manner as in Example 1 except that 0.5 part by weight of triallyl phosphate was replaced with 0.5 part by weight of triallylphosphite represented by the following formula (b) in the preparation of the non-aqueous electrolyte of Example 1 .

[Formula b]

Example  5

A secondary battery was manufactured in the same manner as in Example 2 except that 0.5 part by weight of triallyl phosphate was replaced by 0.5 part by weight of triallyl phosphite represented by the above formula (b) in the preparation of the nonaqueous electrolyte of Example 2 .

Example  6

A secondary battery was manufactured in the same manner as in Example 3 except that 0.5 part by weight of triallyl phosphate was replaced with 0.5 part by weight of triallyl phosphite represented by the above formula (b) in the preparation of the nonaqueous electrolyte of Example 3 .

Comparative Example  One

A lithium secondary battery was prepared in the same manner as in Example 1, except that the addition of triallyl phosphate and perfluorohexane-1,6-dinitrile was omitted in the electrolyte preparation of Example 1 above.

Comparative Example  2

A lithium secondary battery was prepared in the same manner as in Example 1, except that the addition of perfluorohexane-1,6-dinitrile was omitted in the electrolyte preparation of Example 1.

Comparative Example  3

A lithium secondary battery was prepared in the same manner as in Example 4, except that the addition of perfluorohexane-1,6-dinitrile was omitted in the electrolyte preparation of Example 4.

Comparative Example  4

A lithium secondary battery was prepared in the same manner as in Example 1, except that the addition of triallyl phosphite was omitted in the electrolyte preparation process of Example 1.

Comparative Example  5

A lithium secondary battery was prepared in the same manner as in Example 2 except that the addition of triallyl phosphite was omitted in the electrolyte preparation process of Example 2.

Comparative Example  6

A lithium secondary battery was prepared in the same manner as in Example 3, except that the addition of triallyl phosphite was omitted in the electrolyte preparation of Example 3.

[Experimental Example]

Experimental Example  1: Evaluation of high-temperature lifetime characteristics

A battery having a capacity of 910 mAh manufactured using the non-aqueous electrolyte of Examples 1-6 and Comparative Example 1-6 was charged to 4.2 V at 1820 mA (CC / CV) at a high temperature (45 ° C) After discharging to 2.7V at 1820mA (CC), it had a downtime of 10 minutes again. This procedure was repeated 100 times to measure the capacity (mAh) and efficiency (%). The initial capacity and efficiency measured in the following Table 1 and the capacity and efficiency measured after 100 cycles were shown.

1 cycle discharge capacity (mAh) 100 cycle discharge capacity (mAh) efficiency(%) Example 1 919.3 871.0 94.7 Example 2 933.1 878.7 94.2 Example 3 930.2 868.5 93.4 Example 4 922.1 861.4 93.4 Example 5 934.9 870.0 93.1 Example 6 932.8 867.1 93.0 Comparative Example 1 926.0 850.0 91.8 Comparative Example 2 926.4 849.0 91.7 Comparative Example 3 923.4 846.9 91.7 Comparative Example 4 928.2 850.8 91.7 Comparative Example 5 928.7 850.8 91.6 Comparative Example 6 932.8 853.7 91.5

As shown in Table 1, the lithium secondary batteries (Examples 1 to 6) according to the present invention had better 100-cycle discharge capacity and efficiency at high temperature (45 ° C) than Comparative Examples 1 to 6 Can be confirmed. Particularly, it can be confirmed that Example 1 using triallyl phosphite and perfluoropec-acid-1,6-dinitrile in combination in the production of a non-aqueous electrolyte has the best high-temperature lifetime characteristics.

In addition, referring to the results of Comparative Examples 1 to 6, in the case of Comparative Examples 2 to 6 in which only one of the phosphorus compound and the organic fluorine compound was used, the efficiency and the discharge capacity as compared with Comparative Example 1, Can be confirmed.

Experimental Example  2: Evaluation of recovery capacity by high temperature neglect

A 910 mAh battery manufactured using the non-aqueous electrolyte of Example 1-6 and Comparative Example 1-6 was charged to 4.2 V at 910 mA (CC / CV) at room temperature (25 ° C) And the discharge capacity was measured. The battery was charged to 4.2 V by the same method, left at 60 ° C. for 30 days, discharged at 2.7 V at room temperature, aged for 1 hour, charged again to 4.2 V, discharged at 2.7 V, ) Were measured. The initial measured capacity and the capacity measured after 30 days of storage are shown in Table 2 and FIG. 2 below.

The initial discharge capacity (mAh) Discharge capacity after 30 days (mAh) efficiency(%) Example 1 928.5 862.7 92.9 Example 2 933.2 864.5 92.6 Example 3 925.4 851.3 92.0 Example 4 929.7 854.1 91.9 Example 5 936.1 857.1 91.6 Example 6 937.3 858.6 91.6 Comparative Example 1 936.0 850.2 90.8 Comparative Example 2 938.1 852.4 90.9 Comparative Example 3 934.8 846.8 90.6 Comparative Example 4 935.0 834.7 89.3 Comparative Example 5 927.2 844.0 91.0 Comparative Example 6 931.2 847.6 91.0

As shown in Table 2 and FIG. 2, the lithium secondary batteries (Examples 1 to 6) made of a non-aqueous electrolyte using a phosphorus compound and an organic fluorine compound in specific combinations had a high temperature ) Is more excellent.

Further, the batteries of Examples 1 to 6, in which the phosphorus compound and the organic fluorine compound were used in combination, had a lower degree of capacity reduction after 30 days of storage at a high temperature than Comparative Examples 1 to 6. In the case of using the non- It can be seen that the recovery capacity can be improved.

Experimental Example  3: Evaluation of the resistance by leaving the high temperature

A 910 mAh battery manufactured using the non-aqueous electrolyte of Example 1-6 and Comparative Example 1-6 was charged to 4.2 V at 910 mA (CC / CV) at room temperature (25 ° C) And the internal resistance was measured. The battery was charged to 4.2 V by the same method, left at 60 ° C. for 30 days, discharged at 2.7 V at room temperature, aged for 1 hour, charged again to 4.2 V, discharged at 2.7 V, Respectively. In Table 3 and FIG. 3, resistance values measured after initial and 30-day standing and their increasing rates are shown.

Initial internal resistance (mΩ) Internal resistance (mΩ) after 30 days Growth rate (%) Example 1 39.2 65.8 168.0 Example 2 39.2 67.2 171.5 Example 3 41.9 73.5 175.6 Example 4 41.4 73.9 178.6 Example 5 39.2 64.9 165.8 Example 6 39.6 66.7 168.3 Comparative Example 1 42.3 89.7 212.0 Comparative Example 2 43.2 85.2 197.1 Comparative Example 3 39.6 73.0 184.4 Comparative Example 4 40.5 71.2 175.9 Comparative Example 5 44.1 96.5 218.7 Comparative Example 6 43.2 92.4 213.8

As shown in Table 3 and FIG. 3, the lithium secondary batteries (Examples 1 to 6) according to the present invention had a higher initial resistance at a high temperature (60 ° C) compared to Comparative Examples 1 to 6, Can be confirmed.

Particularly, it was confirmed that the resistance increase rate was even lower when triallylphosphite and perfluorocerbanonitrile were used in combination (Example 5). The effect of decreasing the rate of resistance increase was obtained when a phosphorus compound and an organic fluorine compound were used in combination And it was confirmed that it was more effective.

Claims (20)

Nonaqueous solvent; Lithium salts; Electrolyte additive; Phosphorus compounds containing at least 3 allyl groups; And an organic fluorine compound containing nitrogen or sulfur, wherein the nitrogen or sulfur-containing organic fluorine compound is contained in an amount of 0.1 to 3% by weight. The method according to claim 1,
Wherein the non-aqueous solvent is a carbonate-based organic solvent or a propionate-based organic solvent. 3. The method of claim 2,
The carbonate-based organic solvent may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC) ), Ethylmethyl carbonate (EMC), methyl ethyl carbonate (MEC), fluoroethylene carbonate (FEC), methyl propyl carbonate (MPC) and ethyl propyl carbonate (EPC) Electrolytic solution. The method of claim 3,
Wherein the carbonate-based organic solvent comprises ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). 5. The method of claim 4,
Wherein the carbonate-based organic solvent comprises 10 to 40 wt% of ethylene carbonate (EC), 15 to 45 wt% of diethyl carbonate (DEC), and 30 to 60 wt% of ethylmethyl carbonate (EMC). The method according to claim 1,
The lithium salt is _{LiPF 6, LiClO 4, LiAsF 6} , LiBF 4, LiBF 6, LiSbF 6, LiAl0 4, LiAlCl 4, LiClO 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 ) A natural number), LiCl, LiI, and LiB (C ₂ O ₄ ) ₂ . The method according to claim 1,
Wherein the lithium salt is contained in an amount of 0.5 to 1.5 M (mol / L). The method according to claim 1,
The electrolyte additive may be selected from the group consisting of lithium bis (fluorosulfonyl) imide, lithium tetrafluoro (oxalato) phosphate, lithium difluorophosphate ), Lithium bis (oxaleto borate), 1,3-propane sultone, 1,3-propene sultone, ethylene Wherein the electrolyte is at least one selected from the group consisting of ethylene sulfates, vinylene carbonates, vinyl ethylene carbonate and fluoro ethylene carbonate. The method according to claim 1,
And the electrolyte additive is contained in an amount of 0.1 to 10% by weight. The method according to claim 1,
Wherein the phosphorus compound containing at least three allyl groups is at least one of triallyl phosphate and triallyl phosphite. The method according to claim 1,
Wherein the phosphorus compound containing at least 3 allyl groups is contained in an amount of 0.1 to 3% by weight. The method according to claim 1,
Wherein the organic fluorine compound containing nitrogen or sulfur is perfluoronitrile compounds, fluorosulton compounds or a mixture thereof. 13. The method of claim 12,
The perfluoronitrile compound is represented by the following general formula
[Chemical Formula 1]

(Wherein, in the general formula (1), n is an integer of 1 to 10). 14. The method of claim 13,
Wherein the perfluoronitrile compound is perfluorohexane-1,6-dinitrile or perfluorosubcononitrile. The non-aqueous electrolyte according to claim 1, wherein the perfluoro nitrile compound is perfluorohexane-1,6-dinitrile or perfluorosubcononitrile. 13. The method of claim 12,
Wherein the perfluoronitrile compound is contained in an amount of 0.1 to 2% by weight. 13. The method of claim 12,
The fluorosulfone compound is represented by the following general formula
(2)

Wherein at least one of R 1, R 2, R 3, R 4, R 5 and R 6 is fluorine and the others are hydrogen or a C 1 -C 6 alkyl group, 1 &gt; to 2 &lt; / RTI &gt; alkyl groups). &Lt; / RTI &gt; 17. The method of claim 16,
Wherein the fluorosulfonic compound is 3-fluoro-1,3-propane sultone. 13. The method of claim 12,
And the fluorosulphon compound is contained in an amount of 0.1 to 3% by weight. anode; cathode; A separator; And a nonaqueous electrolytic solution,
Wherein the anode comprises a cathode active material selected from the group consisting of lithium composite metal oxides and lithium olivine phosphates and wherein the cathode is selected from the group consisting of tin, tin compounds, silicon, silicon compounds, lithium titanate, crystalline carbon, amorphous carbon, Natural graphite, and the non-aqueous electrolyte is the electrolyte according to any one of claims 1 to 18. 20. The method of claim 19,
Wherein the positive electrode active material comprises at least one selected from the group consisting of cobalt, manganese, nickel and iron.

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