KR100856286B1 - Nonflammable non-aqueous electrolyte and secondary battery comprising the same - Google Patents

Abstract

The present invention is a mixed organic solvent comprising a phosphoric acid solvent and a mononitrile solvent; And it relates to a nonaqueous electrolyte containing an electrolyte salt. In addition, the present invention is the non-aqueous electrolyte; anode; cathode; And it relates to a secondary battery comprising a separator.

Since the nonaqueous electrolyte solution of the present invention includes a nitrile-based solvent, the ion conductivity is good, and the flame retardancy is very excellent including a phosphoric acid solvent and an additional fluorinated ether solvent. In addition, the secondary battery of the present invention employing the nonaqueous electrolyte solution can greatly improve the safety of the battery without deteriorating battery performance such as initial charge and discharge capacity and ion conductivity.

Secondary Battery, Non-Aqueous Electrolyte, Lithium Titanium Oxide, Phosphoric Acid, Nitrile, Ether, Flame Retardant

Description

Flame retardant non-aqueous electrolyte and secondary battery comprising same {NONFLAMMABLE NON-AQUEOUS ELECTROLYTE AND SECONDARY BATTERY COMPRISING THE SAME}

1 is a graph showing the measurement results of flame retardancy and ion conductivity of the nonaqueous electrolyte prepared in Examples 1 to 8 and Comparative Examples 1 to 3.

The present invention relates to a flame retardant nonaqueous electrolyte and a secondary battery comprising the same.

In recent years, as the light weight and miniaturization of electric products have increased, the demand for power sources having high energy density has increased, and with the increase of interest in environmental pollution, the development of electric vehicles and hybrid electric vehicles has been increasing. It has been greatly demanded. In accordance with these demands, studies on secondary batteries having high energy density have been actively conducted.

At this time, the lithium secondary battery is an energy storage device having high energy and power as a power source, and has an excellent advantage in that its capacity or operating voltage is higher than that of other batteries. However, such a high energy is a problem of the safety of the battery has a risk of explosion or fire. In particular, in recent years, such a hybrid car that is in the spotlight, because the high energy and output characteristics are required such safety can be seen more and more important.

In general, a lithium secondary battery is prepared by using a material capable of inserting and detaching lithium ions as a positive electrode and a negative electrode, and filling a nonaqueous electrolyte between a positive electrode and a negative electrode, and oxidizing when lithium ions are inserted and desorbed from a positive electrode and a negative electrode. Electrical energy is generated by the reaction and reduction.

The nonaqueous electrolyte solution is composed of a combination of a solute such as an electrolyte salt and a nonaqueous organic solvent. Non-aqueous solvents are required to have high dielectric constant, low viscosity, and high oxidation voltage. Generally, a high dielectric constant cyclic carbonate solvent or lactone solvent and a low viscosity linear carbonate or ether solvent are used. . However, a lithium secondary battery using such a non-aqueous electrolyte has a risk of leakage of electrolyte due to battery breakage, resulting in ignition and combustion when a problem such as an increase in pressure inside the battery occurs.

Thus, various attempts have been made to reduce this risk. According to Japanese Patent Application Laid-Open No. Hei 4-184870 and Japanese Patent Application Laid-Open No. Hei 8-088023, it has been proposed to use a phosphate ester having a nonflammable property in a conventional organic solvent system, and at least one alkyl group. An electrolyte solution having self-extinguishing ability using a phosphate ester in which a hydrogen atom is substituted with halogen has also been proposed. However, in the case of using a conventional carbon-based negative electrode material, the reductive decomposition of the solvent occurs extremely at the surface of the negative electrode, so that the charge and discharge characteristics are severely deteriorated, and the viscosity of the phosphate ester is high, thereby increasing the battery's internal resistance. It can degrade performance.

In addition, according to Japanese Patent Application Laid-Open No. 11-307123, it has also been proposed to improve the flame retardancy of the non-aqueous electrolyte by using fluoro ether (HFE). In the case of HFE, flame retardancy and wettability of the electrode / isolator are good, but practical use is difficult because of high volatility and low solubility of lithium salts.

The present invention is to provide a non-aqueous electrolyte that can improve the safety without deterioration of the battery using a solvent having excellent flame retardancy and a low viscosity and good ion conductivity, and a secondary battery comprising the same.

The present invention is a mixed organic solvent comprising a phosphoric acid solvent and a nitrile solvent; And it provides a nonaqueous electrolyte containing an electrolyte salt.

In addition, the present invention is the non-aqueous electrolyte; anode; cathode; And it provides a secondary battery comprising a separator.

Hereinafter, the present invention will be described in detail.

Non-aqueous electrolyte of the present invention is a mixed organic solvent comprising a phosphate solvent represented by the formula (1) and a nitrile solvent represented by the formula (2); And electrolyte salts.

[Formula 1]

In Formula 1, R ₁ to R ₃ are each independently alkyl having 1 to 10 carbon atoms, at least one fluorine atom substituted alkyl having 1 to 10 carbon atoms, alkoxy having 1 to 10 carbon atoms, and at least one fluorine atom. Aromatic substituted alkoxy having 1 to 10 carbon atoms, aryl having 6 to 12 carbon atoms, at least one fluorine atom Substituted aryl having 6 to 12 carbon atoms, aryloxy having 6 to 12 carbon atoms, or at least one fluorine atom substituted Aryloxy having 6 to 12 carbon atoms.

[Formula 2]

N≡CR ₄

In Formula 2, R ₄ is alkyl having 1 to 10 carbon atoms, at least one fluorine atom substituted alkyl having 1 to 10 carbon atoms, aryl having 6 to 12 carbon atoms or at least one fluorine atom substituted aryl having 6 to 12 carbon atoms.

In addition, the mixed organic solvent included in the nonaqueous electrolyte of the present invention may further include a fluorinated ether solvent represented by the following Chemical Formula 3.

[Formula 3]

R ₅ -OR ₆

In Formula 3, R ₅ and R ₆ are each independently alkyl having 1 to 10 carbon atoms or aryl having 6 to 12 carbon atoms, and at least one of R ₅ and R ₆ is substituted with at least one hydrogen atom by a fluorine atom.

The organic solvent included in the nonaqueous electrolyte of the present invention is a mixed organic solvent of a phosphoric acid solvent which is a flame retardant solvent and a low viscosity mononitrile solvent having good ion conductivity. In addition, the mixed organic solvent may further include a fluorinated ether solvent is a flame retardant solvent.

When the solvent having excellent flame retardancy is used as the organic solvent of the nonaqueous electrolyte, the safety of the battery can be improved. However, the phosphoric acid-based solvent has a high viscosity and when used as a solvent of the electrolyte solution, the internal resistance of the battery increases, which negatively affects battery performance. Therefore, a combination with another solvent for improving the ionic conductivity is required. In this case, when the phosphate-based solvent is used together with a carbonate-based solvent that is commonly used, the effect of improving the ionic conductivity is not large. In the present invention, an electrolyte solution using a nitrile-based solvent of Formula 2 having better ionic conductivity than the carbonate-based solvent is used together. It is characterized by comprising an organic solvent.

In addition, the phosphoric acid solvent and the mononitrile solvent may be substituted with a fluorine atom (F). When the solvent is substituted with a halogen element, the flame retardancy is further increased, but when the solvent is substituted with Cl, Br, or I, the reactivity of the solvent increases together, which is not preferable as an electrolyte solution.

Phosphoric acid-based solvent contained in the mixed organic solvent: nitrile-based solvent = 60 to 95 parts by volume: preferably 5 to 40 parts by volume. If the ratio of the phosphoric acid-based solvent is less than 60 parts by volume, it is difficult to ensure flame retardancy of the electrolyte, and when it is more than 95 parts by volume, the ion conductivity is low, resulting in deterioration of battery performance.

In addition, when the fluorinated ether solvent further includes a fluorinated ether solvent having good flame retardancy in the mixed organic solvent of the phosphoric acid solvent and the nitrile solvent, the fluorinated ether solvent is 100 parts of the total mixed organic solvent of the phosphoric acid solvent and the nitrile solvent. It is preferably included in a ratio of more than 0 to 20 parts by volume with respect to the skin. When the fluorinated ether solvent is included in the mixed organic solvent, the flame retardancy of the electrolyte may be improved. However, since fluorinated ether solvents are volatile and have low solubility for dissolving electrolyte salts, the inclusion of more than 20 parts by volume lowers the ionic conductivity and increases volatility, leading to deterioration of battery performance.

In the non-aqueous electrolyte of the present invention, non-limiting examples of the phosphoric acid solvent represented by the formula (1) include trimethylphosphine oxide, triethylphosphine oxide, tripropylphosphine oxide, triphenylphosphine oxide, diethyl methyl Phosphonate, dimethyl methylphosphonate, diphenyl methylphosphonate, bis (2,2,2-trifluoroethyl) methylphosphonate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, ethyl methyl phenyl Phosphate and the like. These phosphoric acid solvents may be used alone or in combination of two or more thereof.

In addition, non-limiting examples of the nitrile-based solvent represented by Formula 2, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, and the like. These nitrile solvents may be used alone or in combination of two or more thereof.

In addition, non-limiting examples of the fluorinated ether solvent represented by Formula 3 include, but are not limited to, bis-2,2,2-trifluoroethyl ether, n-butyl 1,1,2,2-tetrafluoroethyl ether, 2,2,3,3,3-pentafluoropropyl methyl ether, 2,2,3,3,3-pentafluoropropyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2, 2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, trifluoroethyl dodecafluorohexyl ether, and the like. These fluorinated ether solvents may be used alone or in combination of two or more thereof.

The electrolyte salt contained in the nonaqueous electrolyte is preferably a lithium salt. Non-limiting examples of lithium salts include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ), where x and y are natural numbers, LiSO ₃ CF _3, and the like. These lithium salts can be used individually or in mixture of 2 or more types. In addition, the electrolyte salt may be used in a concentration of 0.8 ~ 2.0 M with respect to the mixed organic solvent.

The secondary battery of the present invention is a positive electrode; cathode; The nonaqueous electrolyte of the present invention; And it may comprise a separator.

The negative electrode may include a lithium titanium oxide represented by the formula Li _a Ti _3-a O ₄ (0 <a <3) as a negative electrode active material. Non-limiting examples of lithium titanium oxide as a negative electrode active material include Li _4/3 Ti _5/3 O ₄ , LiTi ₂ O ₄ , Li _4/5 Ti _11/5 O _4, and the like. Can be mixed and used.

In the secondary battery including the nonaqueous electrolyte of the present invention, when the negative electrode is formed using a carbon-based active material commonly used as a negative electrode active material, a gas obtained by reduction decomposition of the phosphoric acid-based solvent contained in the nonaqueous electrolyte is formed on the surface of the negative electrode. Swelling may occur. Therefore, it is necessary to configure the negative electrode using an active material which does not cause reduction decomposition of the phosphate solvent on the negative electrode surface. Accordingly, the secondary battery of the present invention is characterized by using a lithium titanium oxide represented by the formula Li _a Ti _3-a O ₄ (0 <a <3) as a negative electrode active material.

Electrodes in the present invention can be prepared by conventional methods known in the art. For example, a slurry may be prepared by mixing and stirring a binder and a solvent, a conducting agent, and a dispersant in an electrode active material of the present invention, and then applying the same to a current collector of a metal material, compressing, and drying the electrode. have.

The binder can be suitably used in an amount of 1 to 10 by weight and the conductive agent in an amount of 1 to 30 by weight based on the electrode active material.

The positive electrode active material is not particularly limited as long as the positive electrode active material is an active material capable of inserting and detaching lithium ions, and is normally used as a positive electrode active material for secondary batteries. A lithium transition metal oxide or a chalcogen compound may be used.

Examples of the lithium transition metal oxide include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y O ₂ , LiCo _1-Y Mn _Y O ₂ , LiNi _1-Y Mn _Y O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-z Ni _z O ₄ , LiMn _{2- z} Co _z O ₄ (here, 0 <Z <2), LiCoPO ₄ , LiFePO ₄ or a part of manganese, nickel, cobalt of these oxides substituted with another transition metal or the like or vanadium oxide containing lithium (LiV ₃ O ₈ ). Examples of the chalcogen compound include manganese dioxide, titanium disulfide, molybdenum disulfide, and the like. And these positive electrode active materials can be used individually or in mixture of 2 or more types.

Examples of binders that can be used include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and the like.

Generally, carbon black may be used as the conductive agent, and acetylene black series (such as a Chevron Chemical Company or Gulf Oil Company) may be used as a commercially available product. Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MMM) There is this.

The current collector of the metal material is a metal having high conductivity, and any metal can be used as long as the slurry of the electrode active material can be easily adhered and is not reactive in the voltage range of the battery. Representative examples include meshes and foils made of aluminum, copper, gold, nickel or aluminum alloys or combinations thereof.

The method of applying the slurry to the current collector is also not particularly limited. For example, it can be applied by a method such as doctor blade, dipping, brushing, and the like, but the coating amount is not particularly limited, but the thickness of the active material layer formed after removing the solvent or the dispersion medium is usually 0.005-5 mm, preferably 0.05-2 mm. The amount of the range which becomes a range is preferable.

The method of removing the solvent or the dispersion medium is not particularly limited, but the solvent or the dispersion medium may be used as quickly as possible within the speed range in which stress concentration occurs and cracks occur in the active material layer or the active material layer does not peel off from the current collector. It is preferable to use a method of adjusting to remove to volatilize. As a non-limiting example it may be dried for 0.5 to 3 days in a vacuum oven at 50 ~ 200 ℃.

The secondary battery of the present invention can be prepared by conventional methods known in the art, including the nonaqueous electrolyte of the present invention. For example, a porous separator may be inserted between the positive electrode and the negative electrode to add an electrolyte solution. The secondary battery includes a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

The separator usable in the secondary battery of the present invention is not particularly limited, but it is preferable to use a porous separator, and non-limiting examples include a polypropylene-based, polyethylene-based, or polyolefin-based porous separator.

The secondary battery of the present invention is not limited in appearance, but may be cylindrical, square, pouch type, or coin type using a can.

Hereinafter, the present invention will be described in detail with reference to the following Examples. However, the following examples are only for exemplifying the present invention, and the present invention is not limited by the following examples.

(Example 1)

Trimethyl phosphate (TMP): Butyronitrile (BN) = 50: 50 (v: v) LiPF ₆ was dissolved in a mixed organic solvent to a concentration of 1M to prepare a non-aqueous electrolyte.

95 parts by weight of Li _4/3 Ti _5/3 O ₄ as a negative electrode active material and 5 parts by weight of PVDF as a binder were added to NMP (N-methyl-2-pyrrolidone) to prepare a negative electrode slurry, and then a copper (Cu) current collector phase It was applied to and dried to prepare a negative electrode.

90 parts by weight of LiMn ₂ O ₄ as a positive electrode active material, 5 parts by weight of acetylene black as a conductive agent and 5 parts by weight of PVDF as a binder are added to NMP to prepare a positive electrode slurry, which is then coated on an aluminum (Al) current collector and dried. To prepare a positive electrode.

After interposing a polyolefin-based separator between the prepared positive electrode and negative electrode, the non-aqueous electrolyte was injected to prepare a coin-type lithium secondary battery.

(Example 2)

Trimethyl phosphate (TMP): Butyronitrile (BN) = 60: 40 (v: v) except that a non-aqueous electrolyte was prepared by dissolving LiPF ₆ to 1M concentration in a mixed organic solvent. In the same manner as the battery was prepared.

(Example 3)

Trimethyl phosphate (TMP): Butyronitrile (BN) = 70: 30 (v: v), except that LiPF ₆ dissolved in a mixed organic solvent to a concentration of 1M to prepare a non-aqueous electrolyte solution, The battery was manufactured by the same method as 1.

(Example 4)

Trimethyl phosphate (TMP): Butyronitrile (BN) = 80: 20 (v: v) Except for dissolving LiPF ₆ to a concentration of 1 M to prepare a non-aqueous electrolyte, except that a non-aqueous electrolyte was prepared In the same manner as the battery was prepared.

(Example 5)

Trimethyl phosphate (TMP): Butyronitrile (BN) = 90: 10 except that a non-aqueous electrolyte was prepared by dissolving LiPF ₆ to 1 M in a mixed organic solvent having a composition of (v: v). In the same manner as the battery was prepared.

(Example 6)

Trimethyl phosphate (TMP): butyronitrile (BN): trifluoroethyl dodecafluorohexyl ether (HFE7500) = 70: 20: 10 (v: v: v) LiPF ₆ in a mixed organic solvent having a composition of 1M A battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was prepared by dissolving to a concentration.

(Example 7)

Trimethyl phosphate (TMP): Butyronitrile (BN): Trifluoroethyl dodecafluorohexyl ether (HFE7500) = 70: 25: 5 (v: v: v) 1M LiPF ₆ in a mixed organic solvent composition A battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was prepared by dissolving to a concentration.

(Example 8)

Trimethyl phosphate (TMP): Butyronitrile (BN): Trifluoroethyl dodecafluorohexyl ether (HFE7500) = 75: 20: 5 (v: v: v) LiPF ₆ in a mixed organic solvent having a composition of 1M A battery was manufactured in the same manner as in Example 1, except that the non-aqueous electrolyte was prepared by dissolving to a concentration.

(Comparative Example 1)

Ethylene carbonate (EC): Example 1 except that a non-aqueous electrolyte was prepared by dissolving LiPF ₆ to 1 M in an organic solvent having a composition of ethyl methyl carbonate (EMC) = 1: 2 (v: v). A battery was prepared in the same manner.

(Comparative Example 2)

A battery was manufactured in the same manner as in Example 1, except that LiPF ₆ was dissolved in an organic solvent using trimethyl phosphate (TMP) only at a concentration of 1 M to prepare a nonaqueous electrolyte.

(Comparative Example 3)

Trimethyl phosphate (TMP): ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 5: 2: A solution of LiPF ₆ was dissolved in an organic solvent having a composition of 3 (v: v: v) to a concentration of 1 M to prepare a nonaqueous electrolyte solution. A battery was manufactured in the same manner as in Example 1, except that the battery was prepared.

(Evaluation of initial charge and discharge performance of battery)

Experiments were conducted to evaluate the initial charge and discharge performance and the discharge capacity ratio (%) after 50 cycles of the batteries prepared in Examples 1 to 8 and Comparative Examples 1 to 3, and the results are shown in Table 1 below. .

Charging the battery to 2.75V with 0.1C-rate current and discharging it to 0.1V at 0.1C-rate is called initial charge and discharge, and the ratio of charge capacity to discharge capacity is called efficiency. In addition, charging and discharging with a current of 1.0 C-rate in the same voltage region is called 1 cycle, and this was repeated 50 times.

Charge capacity (mAh) Discharge capacity (mAh) Initial Efficiency (%) Discharge capacity ratio after 50 cycles (%) Example 1 2.32 2.14 92.4 95.5 Example 2 2.24 2.06 92.0 95.6 Example 3 2.37 2.19 92.4 95.3 Example 4 2.36 2.17 92.1 95.3 Example 5 2.39 2.23 93.4 95.1 Example 6 2.37 2.18 92.0 95.4 Example 7 2.30 2.13 92.6 95.6 Example 8 2.39 2.21 92.4 95.6 Comparative Example 1 2.29 2.13 92.7 95.6 Comparative Example 2 2.36 2.18 92.5 78.6 Comparative Example 3 2.34 2.16 92.3 82.9

According to Table 1, the initial charge and discharge capacity and the initial efficiency of Examples 1 to 8 are similar to the initial charge and discharge performance (capacity and initial efficiency) of Comparative Examples 1 to 3, the discharge capacity ratio after 50 cycles or It was found to be improved.

(Evaluation of flame retardancy (self-extinguishing time) and ionic conductivity of electrolyte)

Flame retardancy (self-extinguishing time) and ionic conductivity were measured using the nonaqueous electrolytes prepared in Examples 1 to 8 and Comparative Examples 1 to 3, and the results are shown graphically in FIG. 1.

In the method of measuring the self-extinguishing time, a predetermined amount of the electrolyte was impregnated into the porous nickel plate, and then the ignition time according to ignition was measured.

In addition, the ion conductivity was used Mettler's equipment, and after impregnating the measuring cell in 10 ml of the target electrolyte at room temperature, the ion conductivity was measured when the temperature of the solution is isothermal and room temperature.

According to FIG. 1, it turned out that the flame retardance of the nonaqueous electrolyte solution of Examples 4-8 is very excellent. That is, as the content of trimethyl phosphate was increased, it was also found that the flame retardancy was improved when trifluoroethyl dodecafluorohexyl ether was used.

However, when only trimethyl phosphate was used as the organic solvent of the nonaqueous electrolyte as in Comparative Example 2, the ion conductivity was very low due to the high viscosity of the trimethyl phosphate itself. Therefore, the use of mononitrile-based solvents together was more effective in improving the ionic conductivity than using only trimethyl phosphate as the organic solvent.

In consideration of the flame retardancy and ionic conductivity of FIG. 1, the nonaqueous electrolytes of Examples 2 to 5 were preferred as electrolytes capable of improving safety without deteriorating battery performance. In addition, the nonaqueous electrolyte of Examples 6 to 8 further including the fluorinated ether solvent in the mixed organic solvent of the phosphoric acid solvent and the mononitrile solvent, showed better results than the ionic conductivity measured in the electrolyte solution of Comparative Example. In particular, since the flame retardance of electrolyte solution improved very much, it was more preferable as electrolyte solution.

Since the nonaqueous electrolyte solution of the present invention includes a nitrile-based solvent, the ion conductivity is good, and the flame retardancy is very excellent including a phosphoric acid solvent and an additional fluorinated ether solvent. In addition, the secondary battery of the present invention employing the nonaqueous electrolyte solution can greatly improve the safety of the battery without deteriorating battery performance such as initial charge and discharge capacity and ion conductivity.

Claims (12)

A mixed organic solvent comprising a phosphoric acid solvent represented by Chemical Formula 1 and a nitrile solvent represented by Chemical Formula 2; And Contains an electrolyte salt, The phosphoric acid solvent: nitrile solvent = 60 to 95 parts by volume: 5 to 40 parts by volume of a nonaqueous electrolyte. [Formula 1]

In Chemical Formula 1, R ₁ to R ₃ are each independently alkyl having 1 to 10 carbon atoms, alkyl having 1 to 10 carbon atoms substituted with one or more fluorine atoms, alkoxy having 1 to 10 carbon atoms, or 1 to 1 carbon atoms substituted with at least one fluorine atom. Alkoxy of 10, aryl of 6 to 12 carbon atoms, aryl of 6 to 12 carbon atoms substituted with one or more fluorine atoms, aryloxy of 6 to 12 carbon atoms, or aryloxy of 6 to 12 carbon atoms substituted with one or more fluorine atoms. [Formula 2] N≡CR ₄ In Formula 2, R ₄ is alkyl having 1 to 10 carbon atoms, aryl having 1 to 10 carbon atoms substituted with one or more fluorine atoms, aryl having 6 to 12 carbon atoms or aryl having 6 to 12 carbon atoms substituted with one or more fluorine atoms. The non-aqueous electrolyte according to claim 1, wherein the mixed organic solvent further comprises a fluorinated ether solvent represented by the following Chemical Formula 3. [Formula 3] R ₅ -OR ₆ In Formula 3, R ₅ and R ₆ are each independently alkyl having 1 to 10 carbon atoms or aryl having 6 to 12 carbon atoms, and at least one of R ₅ and R ₆ is substituted with at least one hydrogen atom by a fluorine atom. delete The non-aqueous electrolyte solution of claim 2, wherein the fluorinated ether solvent is included in an amount of more than 0 parts by volume and less than 20 parts by volume with respect to 100 parts by weight of the total mixed organic solvent of the phosphoric acid solvent and the nitrile solvent. The method of claim 1, wherein the phosphoric acid solvent is trimethylphosphine oxide, triethylphosphine oxide, tripropylphosphine oxide, triphenylphosphine oxide, diethyl methylphosphonate, dimethyl methylphosphonate, diphenyl Methylphosphonate, bis (2,2,2-trifluoroethyl) methylphosphonate, trimethyl phosphate, triethyl phosphate, tripropyl phosphate and ethyl methyl phenyl phosphate Nonaqueous electrolyte. The method of claim 1, wherein the nitrile-based solvent is acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, At least one selected from the group consisting of 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile and 4-fluorophenylacetonitrile Nonaqueous electrolyte. The method of claim 2, wherein the fluorinated ether solvent is bis-2,2,2-trifluoroethyl ether, n-butyl 1,1,2,2-tetrafluoroethyl ether, 2,2,3,3 , 3-pentafluoropropyl methyl ether, 2,2,3,3,3-pentafluoropropyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl Non-aqueous electrolyte solution, characterized in that at least one member selected from the group consisting of methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether and trifluoroethyl dodecafluorohexyl ether. The method of claim 1, wherein the electrolyte salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers) and LiSO ₃ CF ₃ Non-aqueous electrolyte solution characterized by the above lithium salt. The nonaqueous electrolyte of claim 1, wherein the electrolyte salt is 0.8 to 2.0 M in concentration with respect to the mixed organic solvent. anode; cathode; The nonaqueous electrolyte of any one of claims 1 to 2 and 4 to 9; And a secondary battery comprising a separator. The secondary battery of claim 10, wherein the negative electrode comprises a lithium titanium oxide represented by the formula Li _a Ti _3-a O ₄ (0 <a <3) as a negative electrode active material. The method of claim 10, wherein the negative electrode is a negative electrode active material of at least one lithium titanium oxide selected from the group consisting of Li _4/3 Ti _5/3 O ₄ , LiTi ₂ O ₄ and Li _4/5 Ti _11/5 O ₄ Secondary battery comprising a.

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