JP5484078B2 - Nonaqueous electrolyte containing fluorine-containing phosphoric ester amide - Google Patents

Description

  The present invention relates to a nonaqueous electrolytic solution containing a fluorine-containing phosphoric ester amide. More specifically, the present invention relates to a nonaqueous electrolytic solution containing a fluorine-containing phosphoric ester amide that is excellent in flame retardancy and battery characteristics as a nonaqueous electrolytic solution.

  Non-aqueous secondary batteries have high output density and high energy density, and are widely used as power sources for mobile phones, personal computers, and the like. In recent years, as a clean energy with low carbon dioxide emission, it has been actively researched as a power storage power source and a power source for electric vehicles.

Non-aqueous secondary batteries include lithium secondary batteries, lithium ion secondary batteries, magnesium secondary batteries, magnesium ion secondary batteries, etc., but here, in particular, lithium secondary batteries and lithium ion secondary batteries are described. To do. In general, a lithium secondary battery or a lithium ion secondary battery uses a material whose main component is a lithium-containing transition metal oxide for a positive electrode. For the negative electrode, a material mainly composed of metallic lithium, lithium alloy, or a carbonaceous material typified by graphite is used. In general, when metallic lithium or a lithium alloy is used for the negative electrode, it is called a lithium secondary battery, and when a carbonaceous material is used, it is called a lithium ion secondary battery. A separator is provided between the positive electrode and the negative electrode, and a non-aqueous electrolyte is filled as a medium in which Li ions move. As this nonaqueous electrolytic solution, a solution obtained by dissolving an electrolyte such as lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent having a high dielectric constant such as ethylene carbonate or dimethyl carbonate is widely used.
Organic solvents used for non-aqueous secondary batteries are volatile and flammable, and are classified as flammable substances. For this reason, a non-aqueous electrolyte solution that is free from the risk of ignition is desired particularly for applications of large non-aqueous secondary batteries such as power storage power sources and electric vehicle power sources. For this reason, a technique using a non-aqueous electrolyte having flame retardancy or self-extinguishing properties has attracted attention.

  Addition of phosphoric acid esters known as flame retardants for resin materials has been studied as a method for making such non-aqueous electrolytes flame retardant (Patent Documents 1 and 2). In particular, fluorine-containing phosphates having a fluorine atom in the ester side chain are known to have a high degree of flame retardancy, and are promising materials for making a battery flame-retardant (Non-Patent Document 1, Patent Document 3, Patent Document 4, Patent Document 5).

  Non-aqueous secondary batteries are required to exhibit not only safety but also high battery performance. However, phosphate esters such as those disclosed in Patent Document 3, Patent Document 4, and Patent Document 5 have problems in battery performance such as a high rate discharge capacity. After all, the battery containing any fluorine-containing phosphate ester does not have sufficient characteristics in battery performance.

JP-A-8-22839 JP-A-11-260401 JP 2007-258067 A JP 2007-141760 A JP 2008-21560 A

J. et al. Electrochem. Soc. , 150, A161 (2003)

  The present invention has been made in view of these problems. That is, an object of the present invention is to provide a non-aqueous electrolyte solution that exhibits high flame retardancy and high battery performance such as high rate charge / discharge characteristics with respect to the electrolyte solution for non-aqueous secondary batteries.

  By adding a fluorine-containing phosphoric ester amide to the electrolytic solution, the present inventors show a high degree of flame retardancy, and surprisingly a non-aqueous system that exhibits high performance in battery performance such as high rate charge / discharge characteristics. The present inventors have found an electrolytic solution and completed the present invention. That is, the present invention has the following gist.

  General formula (1)

(In the formula, R ¹ and R ² represent an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group. R ¹ and R ² may combine to form a ring. ³ and R ⁴ each represents an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group, and R ³ and R ⁴ may combine to form a ring.)
And at least one of R ³ and R ⁴ relates to a nonaqueous electrolytic solution containing a fluorine-containing phosphoric ester amide which is a fluorine-containing alkyl group.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous secondary battery electrolyte solution and non-aqueous secondary battery which exhibit a high flame retardance and a high performance battery characteristic can be provided.

It is a schematic cross section of the non-aqueous secondary battery used by the Example and the comparative example.

  The present invention is described in further detail below.

  The fluorine-containing phosphoric ester amide added to the non-aqueous secondary battery in the present invention is represented by the general formula (1).

In the general formula ^{(1), R 1, R} 2 is an alkyl group or a fluorinated alkyl group of 1 to 5 carbon atoms, R ¹ and R ² may constitute a ring. R ¹ and R ² are, for example, methyl group, ethyl group, n-propyl group, i-propyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group, 2,2-difluoroethyl group, 2, 2,3,3-tetrafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group and the like, and particularly preferred are methyl group, ethyl group and trifluoromethyl group. R ¹ and R ² may be the same or different.
R ³ and R ⁴ are an alkyl group having 1 to 5 carbon atoms or a fluorine-containing alkyl group, and R ³ and R ⁴ may be bonded to form a ring. R ³ and R ⁴ are, for example, methyl group, ethyl group, n-propyl group, i-propyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, 2,2,3,3 -Tetrafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group, etc., especially 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, 2,2,3 , 3-tetrafluoropropyl group or 2,2,3,3,3-pentafluoropropyl group is preferable. R ³ and R ⁴ may be the same or different.

Examples of such fluorine-containing phosphoric ester amides include bis (2,2,2-trifluoroethyl) dimethylamide phosphate, bis (2,2,2-trifluoroethyl) methylethylamide phosphate, and bisphosphate phosphate. (2,2,2-trifluoroethyl) bis (2,2,2-trifluoromethyl) amide, bis (2,2,2-trifluoroethyl) diethylamide, ethyl phosphate (2,2,2) -Trifluoroethyl) dimethylamide, ethyl phosphate (2,2,2-trifluoroethyl) diethylamide, bis (2,2-difluoroethyl) dimethylamide phosphate, bis (2,2-difluoroethyl) methyl phosphate Ethylamide, bis (2,2-difluoroethyl) bis (2,2,2-trifluoromethyl) amide phosphate, bis (2,2-phosphate) Fluoroethyl) diethylamide, ethyl phosphate (2,2-difluoroethyl) dimethylamide, ethyl phosphate (2,2-difluoroethyl) diethylamide, ethyl phosphate (2,2,2-trifluoroethyl) diethylamide, phosphoric acid (2,2-difluoroethyl) (2,2,2-trifluoroethyl) dimethylamide, phosphoric acid (2,2-difluoroethyl) (2,2,2-trifluoroethyl) diethylamide, bis (2 , 2,3,3-tetrafluoropropyl) dimethylamide, bis (2,2,3,3-tetrafluoropropyl) diethyl phosphate, bis (2,2,3,3,3-pentafluoropropyl) phosphate Dimethylamide, bis (2,2,3,3,3-pentafluoropropyl) diethyl phosphate, phosphoric acid ( , 2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) dimethylamide, phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) ) Diethylamide and the like can be mentioned. Among these fluorine-containing phosphoric ester amides, in general formula (1), R ¹ and R ² are each a methyl group or an ethyl group, and R ³ and R ⁴ are each a 2,2-difluoroethyl group, 2 , 2,2-trifluoroethyl group, 2,2,3,3-tetrafluoropropyl group, or 2,2,3,3,3-pentafluoropropyl group is preferable, for example, phosphoric acid Bis (2,2,2-trifluoroethyl) dimethylamide, bis (2,2,2-trifluoroethyl) diethyl phosphate, bis (2,2-difluoroethyl) dimethylamide phosphate, bis (2 , 2-difluoroethyl) diethylamide, phosphoric acid (2,2-difluoroethyl) (2,2,2-trifluoroethyl) dimethylamide, phosphoric acid (2,2-difluoroethyl) ) (2,2,2-trifluoroethyl) diethylamide, bis (2,2,3,3-tetrafluoropropyl) dimethylamide phosphate, bis (2,2,3,3,3-pentafluorophosphate) Propyl) dimethylamide, phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) dimethylamide, phosphoric acid (2,2,3,3-tetrafluoropropyl) ( 2,2,2-trifluoroethyl) diethylamide.
Phosphoric ester amide has a flame retardant effect even if fluorine does not contain it, but the flame retardant performance is further improved by containing fluorine atoms. In particular, the case where the fluorine content in the phosphoric ester amide is 30 wt% or more is preferable because it exhibits high flame retardancy.

  By adding fluorine-containing phosphoric ester amide to the electrolyte for non-aqueous secondary batteries, in addition to high flame retardancy, non-aqueous secondary batteries have high rate charge / discharge characteristics, low temperature charge / discharge characteristics, cycle Exhibits excellent properties.

  These fluorine-containing phosphoric ester amides are desirably highly pure, and in particular, the content of protic compounds such as water, acid, and alcohol is preferably less than 30 ppm, particularly preferably less than 1 ppm. . Moreover, these fluorine-containing phosphoric ester amides may be used alone or in combination of two or more for non-aqueous electrolytes.

As a method for producing these fluorine-containing phosphoric ester amides, fluorine phosphoric ester amides in the case where R ³ and R ⁴ are the same in general formula (1) are described in, for example, J. Org. Fluor. Chem. 113, 65 (2002); Fluor. Chem. 106, 153 (2000) and J.A. Fluor. Chem. 104, 215 (2000).

Fluorophosphate amides in the case where R ³ and R ⁴ are different in the general formula (1) are, for example, J. Org. Chem. , 19, 1124 (1954), or the aforementioned J. et al. Fluor. Chem. 113, 65 (2002); Fluor. Chem. 106, 153 (2000) and J.A. Fluor. Chem. 104, 215 (2000).

  Next, the non-aqueous electrolyte containing the fluorine-containing phosphoric ester amide of the present invention will be described.

  The above-mentioned fluorine-containing phosphoric ester amide is mixed with another organic solvent and used as a nonaqueous electrolytic solution. As the organic solvent at this time, for example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, cyclic esters such as γ-butyrolactone, γ-valerolactone, propiolactone, dimethyl carbonate, diethyl carbonate, Chain carbonates such as ethyl methyl carbonate and diphenyl carbonate; chain esters such as methyl acetate and methyl butyrate; ethers such as tetrahydrofuran, 1,3-dioxane, dimethoxyethane, diethoxyethane, methoxyethoxyethane, and methyldiglyme; Examples thereof include nitriles such as acetonitrile and benzonitrile, dioxolane or a derivative thereof alone or a mixture of two or more thereof. The amount of fluorine-containing phosphoric ester amide added to these organic solvents is 1 to 50%, preferably 5 to 30%, by weight. When the addition amount is small, the flame retarding effect of the electrolytic solution is not sufficient, and when it exceeds 50%, battery performance may be deteriorated, which is not preferable.

As the electrolyte salt constituting the nonaqueous electrolytic solution, a lithium salt that is stable in a wide potential region can be used. Examples of the electrolyte salt include LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ). ₃ etc. are mentioned. These may be used alone or in combination of two or more. In order to improve the high rate charge / discharge characteristics of the battery, it is desirable that the concentration of the electrolyte salt in the non-aqueous electrolyte is in the range of 1 to 2.5 mol / L.

  The non-aqueous secondary battery using the electrolytic solution of the present invention is a battery comprising at least a positive electrode, a negative electrode, and a separator. The non-aqueous secondary battery using the electrolytic solution of the present invention is not particularly limited in shape, form, etc. It can be arbitrarily selected from a cylindrical shape, a square shape, a coin shape, a card shape, and a large size. In the present specification, lithium or lithium ion secondary batteries are mainly described. However, the present invention is not limited to lithium or lithium ion batteries, but other nonaqueous secondary batteries such as magnesium secondary batteries and magnesium ion secondary batteries. It can also be applied to.

  Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to the examples.

Reference Example 1 Synthesis of bis (2,2,2-trifluoroethyl) dimethylamide phosphate After mixing 340 g of phosphorus trichloride, 184 g of t-butyl alcohol and 496 g of 2,2,2-trifluoroethanol at 0 ° C., The reaction was carried out at 60 ° C. for 3 hours. Subsequently, it cooled to 0 degreeC and 193g of chlorine gas was blown in in 6 hours. Next, 167 g of dimethylamine was added to the reaction solution and reacted at 0 ° C. for 4 hours. After raising the temperature to room temperature, 500 g of water and 16 g of sodium bicarbonate were added to the reaction solution and stirred, and then the aqueous layer was removed. The organic layer was purified by distillation to obtain 630 g of bis (2,2,2-trifluoroethyl) dimethylamide phosphate.

Reference Example 2 Synthesis of bis (2,2-difluoroethyl) dimethylamide phosphate 340 g of phosphorus trichloride, 184 g of t-butyl alcohol and 407 g of 2,2-difluoroethanol were mixed at 0 ° C. and then reacted at 60 ° C. for 3 hours. I let you. Subsequently, it cooled to 0 degreeC and 193g of chlorine gas was blown in in 6 hours. Next, chloroform 500g and dimethylamine 167g were added to the reaction liquid, and it was made to react at 0 degreeC for 4 hours. After raising the temperature to room temperature, 500 g of water and 16 g of sodium bicarbonate were added to the reaction solution and stirred, and then the aqueous layer was removed. The organic layer was purified by distillation to obtain 616 g of bis (2,2,2-trifluoroethyl) dimethylamide phosphate.

Reference Example 3 Synthesis of phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) diethylamide 340 g of phosphorus trichloride and 184 g of t-butyl alcohol, 2,2,3,3 -After reacting 327 g of tetrafluoropropanol and 248 g of 2,2,2-trifluoroethanol at 0 ° C, the mixture was reacted at 60 ° C for 3 hours. Subsequently, it cooled to 0 degreeC and 196g of chlorine gas was blown in in 6 hours. Next, 272 g of diethylamine was added to the reaction solution and reacted at 0 ° C. for 4 hours. After cooling, 500 g of water and 16 g of sodium bicarbonate were added to the reaction solution and stirred, and then the aqueous layer was removed. The organic layer was purified by distillation to obtain 220 g of phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) diethylamide.

The flammability and battery test methods and evaluation methods are shown below.
The combustion test method is shown below.

After adding 5 to 60% by weight of various phosphates in a 1: 1: 1 volume ratio mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, LiPF ₆ is dissolved at a rate of 1 mol / L and non-aqueous electrolysis is performed. The liquid was adjusted.
The test piece in which the above electrolyte solution was impregnated into the glass filter was exposed to a test flame for 10 seconds, and then the test flame was moved away and the state of combustion was observed visually. This test was performed 10 times to evaluate the flammability of each electrolyte.

  The battery test method is shown below.

A non-aqueous secondary battery as shown in the sectional view of FIG. 1 was prepared. The negative electrode 1 was obtained by applying a mixture of graphite and polyvinylidene fluoride N-methyl-2-pyrrolidone to a current collector 2 made of copper foil, drying, and pressure molding, and the positive electrode 3 was LiCoO 2. And a mixture of acetylene black and N-methyl-2-pyrrolidone applied to the current collector 4 made of aluminum foil, dried, and then obtained by pressure molding. The materials constituting these negative electrode 1 and positive electrode 3 were laminated via a porous separator 5 (thickness 16 μm, porosity 50%) made of polyethylene. Various phosphoric acid esters were added in an amount of 10 to 60% by weight to a solvent in which ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate were mixed at a volume ratio of 1: 1: 1, and LiPF ₆ was dissolved at a rate of 1.0 mol / L. The thing was made into electrolyte solution. This was impregnated and sealed to prepare a non-aqueous secondary battery.

  Using the battery, initial discharge capacity measurement, high rate discharge capacity measurement, cycle life test, and discharge capacity measurement at low temperature were performed.

  The initial discharge capacity was a constant current constant voltage charge with a current of 10 mA and a final voltage of 4.2 V at 20 ° C., and then a constant current discharge with a current of 2 mA and a final voltage of 2.7 V was performed at 20 ° C. to obtain an initial discharge capacity. .

  The high rate discharge capacity is a constant current constant voltage charge at 20 ° C. with a current of 10 mA and a final voltage of 4.2 V, and then at 20 ° C., a constant current discharge with a current of 30 mA and a final voltage of 2.7 V is performed. It was.

  In the cycle life test, a constant current / constant voltage charge with a current of 10 mA and a final voltage of 4.2 V was performed at 20 ° C., and then a constant current discharge with a current of 2 mA and a final voltage of 2.7 V was performed at 200 ° C. for 200 cycles. . The 200th discharge capacity ratio with respect to the initial discharge capacity was defined as a cycle maintenance ratio.

  The discharge capacity at low temperature was measured by carrying out constant current constant voltage charging at -20 ° C. with a current of 10 mA and a final voltage of 4.2 V, followed by constant current discharge with a current of 2 mA and a final voltage of 2.7 V at 20 ° C.

  The results of conducting the combustion test and the battery test with each phosphate ester-containing electrolyte are shown below as examples and comparative examples.

Example 1 Bis (2,2,2-trifluoroethyl) dimethylamide phosphate Addition 5wt%
In the above combustion test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was selected as the phosphate ester to be added, and the amount added was evaluated at 5% by weight. did.

  In the above battery test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was selected as the phosphate ester to be added, and the addition amount was evaluated at 5% by weight. As a result, the initial discharge capacity was 10.5 mAh, The high rate discharge capacity was 8.3 mAh, the cycle maintenance rate was 93%, and the -20 ° C discharge capacity was 6.3 mAh.

Example 2 Bis (2,2,2-trifluoroethyl) dimethylamide phosphate Amount 10 wt%
In the above combustion test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the amount added was evaluated at 10% by weight. As a result, the product was burned twice.

  In the above battery test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the amount of addition was evaluated at 10% by weight. As a result, the initial discharge capacity was 10.3 mAh, The high-rate discharge capacity was 8.1 mAh, the cycle maintenance rate was 92%, and the −20 ° C. discharge capacity was 5.7 mAh.

Example 3 Bis (2,2,2-trifluoroethyl) dimethylamide phosphate Amount 20 wt%
In the above combustion test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, no combustion occurred.

  In the battery test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the result was evaluated at an addition amount of 20% by weight. As a result, the initial discharge capacity was 10.1 mAh, The high rate discharge capacity was 7.8 mAh, the cycle maintenance rate was 91%, and the −20 ° C. discharge capacity was 5.4 mAh.

Example 4 Bis (2,2,2-trifluoroethyl) dimethylamide phosphate Amount 50 wt%
In the above combustion test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 50% by weight. As a result, no combustion occurred.

  In the battery test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the amount of addition was evaluated at 50% by weight. As a result, the initial discharge capacity was 9.5 mAh, The high rate discharge capacity was 7.2 mAh, the cycle maintenance rate was 88%, and the -20 ° C discharge capacity was 4.8 mAh.

Reference Example 4 Bis (2,2,2-trifluoroethyl) dimethylamide phosphate Addition 60wt%
In the above combustion test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 60% by weight. As a result, no combustion occurred.

  In the above battery test, bis (2,2,2-trifluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 60% by weight. As a result, the initial discharge capacity was 8.6 mAh, The high rate discharge capacity was 6.6 mAh, the cycle maintenance rate was 82%, and the -20 ° C discharge capacity was 3.6 mAh.

Example 5 Bis (2,2-difluoroethyl) dimethylamide phosphate Amount 20 wt%
In the above combustion test, bis (2,2-difluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, no combustion occurred.

  In the above battery test, bis (2,2-difluoroethyl) dimethylamide phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, the initial discharge capacity was 10.2 mAh and high rate discharge. The capacity was 7.9 mAh, the cycle maintenance rate was 91%, and the -20 ° C discharge capacity was 5.5 mAh.

Example 6 Phosphoric acid (2,2-tetrafluoropropyl) (2,2,2-trifluoroethyl) diethylamide Addition 20 wt%
In the above combustion test, phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) diethylamide was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, it did not burn.

  In the above battery test, phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) diethylamide was used as the phosphoric acid ester to be added, and the addition amount was evaluated at 20% by weight. As a result, the initial discharge capacity was 10.1 mAh, the high rate discharge capacity was 7.7 mAh, the cycle retention rate was 92%, and the −20 ° C. discharge capacity was 5.7 mAh.

Comparative Example 1 Phosphoric ester not added In the above-described combustion test, the phosphoric acid ester was not added.

Comparative Example 2 Tris phosphate (2,2,2-trifluoroethyl) Addition 20wt%
In the above-described combustion test, tris (2,2,2-trifluoroethyl) phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, no combustion occurred.

  In the above battery test, tris phosphate (2,2,2-trifluoroethyl) was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, the initial discharge capacity was 9.5 mAh, and the high rate The discharge capacity was 6.5 mAh, the cycle retention rate was 82%, and the −20 ° C. discharge capacity was 4.8 mAh.

Comparative Example 3 Tris phosphate (2,2,3,3-tetrafluoropropyl) Addition 20wt%
In the above-described combustion test, tris (2,2,2-trifluoroethyl) phosphate was used as the phosphate ester to be added, and the addition amount was evaluated at 20% by weight. As a result, no combustion occurred.

In the above battery test, trisphosphate (2,2,3,3-tetrafluoropropyl) phosphate was used as the phosphate ester to be added, and the amount of addition was evaluated at 20% by weight. As a result, the initial discharge capacity was 9.4 mAh, The high rate discharge capacity was 6.3 mAh, the cycle maintenance rate was 89%, and the -20 ° C discharge capacity was 3.3 mAh.
The table | surface which put together the Example and the comparative example is shown below.

  By containing the fluorine-containing phosphoric ester amide having a specific structure of the present invention in a non-aqueous electrolyte, a non-aqueous secondary battery having flame retardancy and improved battery performance can be obtained and extremely useful. .

1: Negative electrode 2: Current collector 3: Positive electrode 4: Current collector 5: Porous separator 6: Metal resin composite film

Claims (1)

Any of the following non-aqueous electrolytes containing a fluorine-containing phosphoric ester amide.
(1) A nonaqueous electrolytic solution containing 5 to 50% by weight of bis (2,2,2-trifluoroethyl) dimethylamide phosphate.
(2) A nonaqueous electrolytic solution containing 20% by weight of bis (2,2-difluoroethyl) dimethylamide phosphate.
(3) A nonaqueous electrolytic solution containing 20% by weight of phosphoric acid (2,2,3,3-tetrafluoropropyl) (2,2,2-trifluoroethyl) diethylamide.

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