JP2000294281A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To provide a high-capacity, flame-retardant, and highly safe non-aqueous electricity
Provided is a lysate secondary battery. SOLUTION: Contains positive electrode, negative electrode and lithium salt
Non-aqueous electrolyte secondary battery with non-aqueous solvent electrolyte
At least at the end of -CF_TwoH group or
-CFH_Two55% fluorination rate having at least one group
40 to 90% by volume of the acyclic fluorinated ether described above,
5 to 50% by volume of an organic solvent having a dielectric constant of 10 or more.
It is composed. -CF at the end_TwoH group or -CFH_Two
Acyclic having at least one group and having a fluorination rate of 55% or more
Fluorinated ethers such as HCF_TwoCF_TwoCH_TwoO
CF _TwoCF_TwoH, HCF_TwoCF_TwoOCH_TwoCF_Three, CF
_ThreeCF_TwoCH_TwoOCF_TwoCF _TwoH, HCF_TwoCF_TwoCH
_TwoOCHF_TwoAre preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly, to a non-aqueous electrolyte secondary battery having high capacity, flame retardancy and high safety.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries represented by lithium secondary batteries have high capacity, high voltage and high energy density, and therefore, great expectations are placed on their development. .

Conventionally, in this nonaqueous electrolyte secondary battery, lithium or a lithium alloy has been used as a negative electrode active material. When these negative electrode active materials are used, a high capacity can be expected. Internal short-circuit is likely to occur due to the dendrite growth, and therefore, there has been a problem that the battery performance is lowered and the safety is lacking.

Accordingly, it has been proposed to use a carbon-based material capable of doping and undoping lithium ions as a negative electrode active material instead of lithium or a lithium alloy. Among these carbon-based materials, graphite has a high crystallinity. high,
Since a large amount of lithium ions can be doped and de-doped, and a high capacity can be achieved, research is actively conducted for practical use thereof (Japanese Patent Laid-Open No. 8-83609).
JP, JP-A-8-315820, JP-A-9-3
No. 5752, Japanese Patent Application Laid-Open No. 10-140425, etc.).

[0005] Further, since the electrolyte of the non-aqueous electrolyte secondary battery is required to have a high mobility of lithium ions during charge and discharge, cyclic carbonates such as ethylene carbonate and propylene carbonate having high conductivity are required. Organic solvents are mainly used.

A non-aqueous electrolyte secondary battery using an electrolyte containing an organic solvent as a main constituent solvent as described above is inevitably free from danger of ignition or ignition in order to ensure safety. Required. In response to such demands, measures are usually taken to prevent overcharging by a protection circuit or the like so that an internal short circuit does not occur. The problem does not occur.

[0007] However, depending on the case where the capacity is increased or the specifications required by the user, it is a safety test that intentionally assumes abnormal use unless the battery structure is devised sufficiently. When a crush test or a nail penetration test was performed, safety tended to decrease. The crush test and nail penetration test in this abnormal use situation are based on the assumption that the battery is crushed by some kind of intention or accident, and cannot occur under normal use conditions. Even in crush tests and nail penetration tests,
A highly safe battery with no danger of ignition is desired. In particular, when a carbon-based material is used as the negative electrode active material, the carbon-based material can contain a large amount of lithium, and thus is suitable for increasing the capacity.
There is a problem that the risk of ignition and ignition in the event of an abnormality is high because the Joule heat causes a rapid heat generation and a high temperature.

[0008]

In order to solve the above problems, it has been studied to make the electrolyte solution nonflammable. Among them, a fluorine-containing organic solvent is thermally and chemically stable. Attention has been paid to this (JP-A-6-176)
768, JP-A-8-37024, JP-A-8-37024
No. 45544).

However, in response to the demand for higher capacity batteries, high-capacity carbon-based materials have been used as the negative electrode active material, so that the safety of the batteries in the crush test and the nail penetration test as described above has been increased. Therefore, among these fluorinated organic solvents, organic solvents having particularly high safety are desired. In addition, fluorine-containing organic solvents are generally expensive, and most of them use only limited lithium salts because the solubility of lithium salts used as electrolytes in non-aqueous electrolyte secondary battery electrolytes is extremely low. There was a problem that it was not possible. Further, since the electrolyte of the non-aqueous electrolyte secondary battery is required to have high conductivity as described above, a cyclic carbonate capable of dissociating a lithium salt into lithium ions and its counter ions is used as a constituent solvent thereof. Although a systemic organic solvent is used, when this cyclic carbonate-based organic solvent and a fluorine-containing organic solvent are used in combination, there is a problem that the compatibility is reduced and the electrolytic solution is separated into two phases.

The present invention solves the above-mentioned problems of the prior art, and uses an electrolyte solution that is flame-retardant, has high safety, and can be used widely even when a high-capacity carbon-based material is used as a negative electrode active material. It is an object of the present invention to provide a nonaqueous electrolyte secondary battery which has sufficient conductivity, high capacity, high capacity, flame retardancy and high safety, while being able to sufficiently dissolve even the lithium salt.

[0011]

The present invention SUMMARY OF] has been made to solve the above problems, the electrolytic solution, at least, at least one having the fluorination ratio of -CF ₂ H group or -CFH ₂ group at the terminal It contains 55% or more of an acyclic fluorinated ether and an organic solvent having a relative dielectric constant of 10 or more, and the content of the acyclic fluorinated ether in the electrolyte is 40 to 90% by volume, and the relative dielectric constant is 10 or more. Organic solvent content of 5 to 50
By setting the volume%, higher safety can be obtained compared to the conventional electrolytic solution using only carbonates,
An electrolyte with excellent lithium salt solubility and high conductivity was obtained, and based on this, a high-capacity, flame-retardant and highly safe non-aqueous electrolyte secondary battery was found to be obtained. It is.

[0012]

In DETAILED DESCRIPTION OF THE INVENTION The present invention, as described above, the electrolytic solution, at least, end in a -CF ₂ H group or -CFH ₂ group at least one fluorination ratio 55 having%
At least one and acyclic fluorinated ether of the foregoing, the dielectric constant is to contain and 10 or more organic solvents, the present invention is a -CF ₂ H group or -CFH ₂ group at the terminal as described in the first Is characterized by using a non-cyclic fluorinated ether having a fluorination rate of 55% or more to make the electrolytic solution flame-retardant, so that a fluorinated compound having at least one —CF ₂ H group or —CFH ₂ group at its terminal Details will be described from the acyclic fluorinated ether having a ratio of 55% or more.

In the present invention, -CF is added to the terminal._TwoH or
-CFH_Two55% fluorination rate having at least one group
Examples of the above acyclic fluorinated ether include, for example, HC
F_TwoCF_TwoCH_TwoOCF_TwoCF_TwoH (1,1,2,2-
Tetrafluoroethyl-2,2,3,3-tetrafluoro
Propyl ether: fluorination rate = about 67%), HCF
_TwoCF_TwoOCH_TwoCF_Three(1,1,2,2-tetraflu
Oromethyl-2,2,2-trifluoroethyl ether
Fluorination rate = 70%), CF_ThreeCF_TwoCH_TwoOCF
_TwoCF_TwoH (2,2,3,3,3-pentafluoropro
Pill-1,1,2,2-tetrafluoroethyl ether
Fluorination rate = about 83%), HCF_TwoCF _TwoCH_TwoO
CHF_Two(2,2,3,3-tetrafluoropropyl-
Difluoromethyl ether: fluorination rate = 60%)
Is mentioned. However, it is limited to only the above examples
Never. The fluorination rate is defined as ether oxygen.
Percentage of hydrogen in adjacent organic groups replaced by fluorine
Yes, for example, HCF_TwoCF_TwoCH_TwoOCF_TwoCF_TwoH
In the formula, the number that can be replaced with H or F is 12,
Since the fluorine substitution number is 8, the fluorination rate is about 67%
It is. In the present invention, the above-mentioned acyclic fluorinated ether
Can be used alone, or two kinds
The above may be used in combination.

The acyclic fluorinated ether having a fluorination rate of 55% or more has high flame retardancy, and when used as an electrolyte, suppresses combustion of the electrolyte under abnormal conditions to enhance safety. effective. If the fluorination rate is not more than 55%, sufficient flame retardancy cannot be obtained, and the higher the fluorination rate, the higher the flame retardancy.
The content is preferably 0% or more, particularly 70% or more, but if it exceeds 95%, the cost becomes too high. Therefore, it is preferably 95% or less, more preferably 90% or less. And, as the organic group adjacent to the ether oxygen of the acyclic fluorinated _{ethers, - (CF 2) n -CF} 2 H (n = 1~6), - (C
F ₂ ) _n —CFH ₂ (n = 1 to 6), —CH ₂ — (CF
_{2) m -CF 2 H (m} = 0~5), - CH 2 - (C
F ₂ ) _m -CFH ₂ (m = 0 to 5) and the like are preferable.

In the present invention, when an acyclic fluorinated ether having a fluorination rate of 55% or more and having at least one —CF ₂ H group or —CFH ₂ group at the terminal is used,
Dielectric constant of 10 to which cyclic carbonate based organic solvent belongs
Even if the above organic solvents are used in combination, without causing separation,
The reason why a uniform electrolyte is obtained is not always clear at present, but probably because at least one terminal of the acyclic fluorinated ether is present in a form leaving hydrogen, all terminal groups are fluorinated. It is considered that this is because the affinity for the organic solvent having the relative dielectric constant of 10 or more is improved because the affinity for the organic solvent is higher than that of the fluorocarbon group.

[0016] However, the fluorination ratio of 55% having at least one -CF ₂ H group or -CFH ₂ group at a terminal
The acyclic fluorinated ether described above has a problem that the dielectric constant is extremely low as an electrolyte solution solvent for a non-aqueous electrolyte secondary battery, and that a lithium salt can hardly be dissolved by itself. Therefore, in the present invention, separation of the electrolytic solution is caused by preparing an electrolytic solution by using an organic solvent having a relative dielectric constant of 10 or more in combination with the acyclic fluorinated ether and dissolving a lithium salt in the mixed solvent. Instead, the electrolyte was made flame-retardant while maintaining sufficient electric conductivity, so that a high-capacity and highly safe non-aqueous electrolyte secondary battery was obtained.

That is, the use of only the acyclic fluorinated ether as described above lowers the dielectric constant required for the electrolytic solution, resulting in a decrease in capacity. for that reason,
By using an organic solvent having a relative dielectric constant of 10 or more, the dielectric constant of the electrolytic solution can be improved. In order to further increase the compatibility between the organic solvent having a relative dielectric constant of 10 or more and the acyclic fluorinated ether, an acyclic carbonate may be contained in the electrolytic solution.

In the present invention, the content of the above-mentioned acyclic fluorinated ether in the electrolytic solution is determined by making the electrolytic solution flame-retardant,
In order to ensure safety even when a high-capacity negative electrode active material is used, it is necessary that the content be 40% by volume or more in the electrolytic solution, and preferably 50% by volume or more. Considering the solubility of the lithium salt, 90% by volume
Or less, and preferably 80% by volume or less.

In the present invention, examples of the organic solvent having a relative dielectric constant of 10 or more include a cyclic carbonic acid ester and a phosphoric acid triester. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the phosphoric acid triester include trimethyl phosphate and tributyl phosphate. Particularly, when a phosphoric acid triester is used, it is preferable because it itself has high flame retardancy and can improve safety. Among them, trimethyl phosphate is most preferable because it is inexpensive and nonflammable.
These organic solvents having a relative dielectric constant of 10 or more can be used alone or in combination of two or more. In particular, when phosphate triesters are used, they are preferably used in combination with cyclic carbonates because they have a lower dielectric constant than cyclic carbonates.

The content of the organic solvent having a relative dielectric constant of 10 or more in the electrolytic solution is set to 5% by volume or more in order to improve the dielectric constant of the electrolytic solution when the acyclic fluorinated ether is used. It is necessary, 10% by volume or more is preferable,
On the other hand, when the content is too large, the dielectric constant is improved, but the safety is reduced. Therefore, the content needs to be 50% by volume or less, and preferably 40% by volume or less.

In the present invention, the relative permittivity of the organic solvent is specified to be 10 or more. When the relative permittivity is less than 10, the decrease in the permittivity due to the use of the acyclic fluorinated ether is prevented. This is because the dielectric constant of the electrolytic solution cannot be improved by suppressing the specific dielectric constant. The specific dielectric constant may be high, and a dielectric constant of up to about 200 can be used.

In the present invention, examples of the acyclic carbonate include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate and the like. These can be used alone or in combination of two or more. They can be used together.

The acyclic carbonate has an effect of increasing the compatibility between the acyclic fluorinated ether and an organic solvent having a relative dielectric constant of 10 or more. However, when the amount of the acyclic carbonate increases, the safety decreases. And its content in the electrolyte is preferably 10% by volume or less,
It is more preferable that the content be not more than volume%.

In preparing the electrolytic solution, the above-mentioned acyclic fluorinated ether and an organic solvent having a relative dielectric constant of 10 or more, if necessary, include the above-mentioned acyclic carbonate, for example, 1,2-dimethoxyethane, , 2-diethoxyethane, γ-butyrolactone, tetrahydrofuran,
1,3-dioxolane or the like can be used, and these may be used alone or in combination of two or more.

The electrolytic solution is prepared by dissolving the lithium salt described below in the above-mentioned solvent. However, since the volume of the lithium salt when dissolved in the solvent is extremely small, the volume of the electrolytic solution is limited to the volume of the constituent solvent. Can be considered to be the same as the total volume of

In the present invention, as an electrolyte of the electrolytic solution, an inorganic lithium salt which has been conventionally difficult to use from the viewpoint of solubility when a fluorine-based organic solvent is used can also be used. Examples of the inorganic lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ and LiCl
O ₄ , LiSbF _{6 and the} like can be mentioned, and these can be used alone or in combination of two or more. Among these inorganic lithium salts, LiPF ₆ and LiAsF, which are relatively inexpensive and have a high degree of dissociation, are used.
₆ , LiBF ₄ , LiClO _4, etc.
F ₆ is particularly preferred. Furthermore, in the present invention, a fluorinated organic lithium salt can be used as the electrolyte of the electrolytic solution, in addition to the inorganic lithium salt. Such fluorinated organic lithium salts include, for example, LiCF ₃
SO ₃ , LiC ₄ F ₉ SO ₃ , LiCF ₃ CO ₂ , Li
₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ ,
LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n
≧ 2), and LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group]. Each of these lithium salts can be used alone,
Although more than one kind can be used in combination, the concentration of the lithium salt in the electrolytic solution is not particularly limited, but is preferably 0.5 to 2 mol / liter, particularly preferably 0.8 to 1 in terms of electric characteristics. 0.5 mol / l is preferred.

In the present invention, as the positive electrode active material, for example, lithium cobalt oxide such as LiCoO ₂ ;
LiMn oxide such as iMn ₂ O ₄ , LiNi
Lithium nickel oxide such as O ₂ , N of LiNiO ₂
LiNi _1-x Co _x O ₂ in which i is partially substituted with Co; metal oxides such as manganese dioxide, vanadium pentoxide, and chromium oxide; and metal sulfides such as titanium disulfide and molybdenum disulfide. , Can be used alone or in combination of two or more. Among these, in particular, LiCoO ₂ , LiN
When a lithium composite oxide, such as iO ₂ , LiNi _1-x Co _x O ₂ , or LiMn ₂ O _4, whose open circuit voltage during charging is 4 V or more on the basis of Li is used as the positive electrode active material, a high energy density is obtained. Is preferred. In addition, even when a thermally unstable lithium nickel oxide or a composite oxide containing nickel is used, the present invention can ensure safety. It is particularly useful when applied when using an active material.

The positive electrode may comprise, as necessary, a conductive auxiliary such as flake graphite, acetylene black, carbon black, and the like, and a polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene dientene polymer. A binder such as is added and mixed to prepare a positive electrode mixture, which is dispersed in a solvent to form a paste (the binder may be dissolved in a solvent in advance and then mixed with a positive electrode active material or the like). The agent-containing paste is applied to a positive electrode current collector made of a metal foil or the like, dried, and formed through a step of forming a positive electrode mixture layer on at least a part of the positive electrode current collector. However, the manufacturing method of the positive electrode
The present invention is not limited to the method described above, but may be another method.

In the present invention, as the negative electrode active material, any material capable of doping / dedoping lithium ions may be used. Specific examples of such a negative electrode active material include, for example,
Carbon materials such as graphite, pyrolytic carbons, cokes, glassy carbons, baked organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon, etc.
Compounds such as alloys such as i, Sn, and In and oxides that can be charged and discharged at a low potential close to Li can be used. These negative electrode active materials can be used alone or in combination of two or more. Can be. In particular, the present invention
Even when a carbon-based material having a (002) plane-to-plane distance (d ₀₀₂ ) of 0.34 nm or less capable of increasing the capacity is used as the negative electrode active material, a highly safe battery can be obtained. The invention is particularly useful when applied to a battery using such a carbon-based material as a negative electrode active material.

For the negative electrode, for example, a binder similar to that of the positive electrode is added to the negative electrode active material, if necessary, and if necessary, a conductive auxiliary such as flake graphite, carbon black, or acetylene black. A negative electrode mixture is prepared by mixing and mixing the mixture into a paste, and then dispersed in a solvent to form a paste (the binder may be dissolved in a solvent in advance and then mixed with the negative electrode active material). The paste containing the agent is applied to a negative electrode current collector made of copper foil or the like, dried, and formed to form a negative electrode mixture layer on at least a part of the negative electrode current collector. However, the method for producing the negative electrode is not limited to the method exemplified above, and may be another method.

As the above-mentioned positive electrode current collector and negative electrode current collector, for example, metal foils such as aluminum foil, copper foil, nickel foil, stainless steel foil and the like, and nets of these metals are used. In particular, aluminum foil is suitable for the positive electrode current collector, and copper foil is suitable for the negative electrode current collector.

The separator is not particularly limited, but preferably has sufficient strength and can hold a large amount of electrolyte.
A microporous film or nonwoven fabric made of polypropylene, polyethylene, or a copolymer of propylene and ethylene having a pore size of 30 to 70% with a pore size of 0 μm is preferable.

[0033]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 A non-cyclic fluorinated ether having at least one terminal group of -CF ₂ H or -CFH ₂ and having a fluorination rate of 55% or more was HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (1,
1,2,2-tetrafluoroethyl-2,2,3,3-
Tetrafluoropropyl ether: fluorination rate: about 67
%), Ethylene carbonate (relative dielectric constant: 90) as an organic solvent having a relative dielectric constant of 10 or more, methylethyl carbonate as an acyclic carbonate, and HCF ₂ CF ₂ CH ₂ OCF ₂ CF _2. H, ethylene carbonate and methyl ethyl carbonate are mixed at a volume ratio of 70:20:10, and LiPF ₆
Was dissolved in 1.0 mol / liter to prepare an electrolytic solution.
The obtained electrolyte was a homogeneous phase, and no separation of the electrolyte was observed.

Separately, flaky graphite was added to LiCoO ₂ as a conductive aid at a weight ratio of 100: 7 and mixed, and this mixture was mixed with a solution obtained by dissolving polyvinylidene fluoride as a binder in N-methylpyrrolidone. Was mixed into a paste. After passing the positive electrode mixture-containing paste through a 70-mesh net to remove large pieces, the paste was uniformly applied to both sides of a positive electrode current collector made of aluminum foil having a thickness of 20 μm and dried to form a positive electrode mixture. After a layer was formed and rolled by a roller press, the lead body was welded to produce a belt-shaped positive electrode.

Next, a non-graphitizable carbon material [(002)
A distance between surfaces (d ₀₀₂ ): 0.335 nm] and a solution in which polyvinylidene fluoride as a binder was dissolved in N-methylpyrrolidone were mixed to form a paste. The paste containing the negative electrode mixture was passed through a 70-mesh net to remove large pieces, and then uniformly applied to both sides of a negative electrode current collector made of a copper foil having a thickness of 10 μm and dried to form a negative electrode mixture. After a layer was formed and rolled by a roller press, the lead body was welded to produce a strip-shaped negative electrode.

The above-mentioned strip-shaped positive electrode is overlaid on the strip-shaped negative electrode via a separator made of a microporous polypropylene film having a thickness of 25 μm, and spirally wound into a spiral electrode body. The battery was filled in a bottom cylindrical battery case, and the positive and negative electrode leads were welded.

Next, 3.6 ml of the above-mentioned electrolytic solution was poured into the battery case, and after the electrolytic solution had sufficiently penetrated into the separator and the like, sealing was performed, preliminary charging and aging were performed, and a cylindrical tube having the structure shown in FIG. Was manufactured.

Referring to the battery shown in FIG. 1, reference numeral 1 denotes the positive electrode and 2 denotes the negative electrode. However, FIG. 1 does not show a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 in order to avoid complication. And
The positive electrode 1 and the negative electrode 2 are spirally wound via a separator 3, and are housed in a battery case 5 together with the electrolytic solution 4 as a spiral electrode body.

The battery case 5 is made of stainless steel, and an insulator 6 made of polypropylene is disposed on the bottom of the battery case 5 before the spiral electrode body is inserted. The sealing plate 7
It is made of aluminum and has a disk shape, a thin portion 7a is provided at the center thereof, and a hole is provided around the thin portion 7a as a pressure introduction port 7b for applying an internal pressure of the battery to the explosion-proof valve 9. ing. The projection 9a of the explosion-proof valve 9 is welded to the upper surface of the thin portion 7a to form a welded portion 11. In addition, the thin portion 7a provided on the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 are illustrated only in a cut plane so as to be easily understood in the drawings, and a contour line behind the cut plane is shown. Is not shown. Also, the thin portion 7a of the sealing plate 7
Also, the welded portion 11 of the protruding portion 9a of the explosion-proof valve 9 is shown in an exaggerated state than it is for easy understanding in the drawings.

The terminal plate 8 is made of rolled steel, nickel-plated on its surface, and has a hat-like shape with a brim-shaped peripheral portion. The terminal plate 8 is provided with a gas outlet 8a. . The explosion-proof valve 9 is made of aluminum and has a disk shape.
In the center thereof, a protruding portion 9a having a tip portion is provided on the power generation element side (the lower side in FIG. 1), and a thin portion 9b is provided, and the lower surface of the protruding portion 9a is closed as described above. It is welded to the upper surface of the thin portion 7a of the plate 7 to form a welded portion 11. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is disposed above the peripheral portion of the sealing plate 7, and the explosion-proof valve 9 is disposed above the insulating packing 10. The insulating packing 10 insulates the sealing plate 7 from the explosion-proof valve 9. The gap between the two is sealed so that the electrolyte does not leak from between the two. The annular gasket 12 is made of polypropylene, and the lead body 13 is made of aluminum. The sealing plate 7 and the positive electrode 1 are connected to each other. An insulator 14 is disposed above the spiral electrode body. The bottom portion is connected by a lead body 15 made of nickel.

Example 2 A non-cyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ group at the terminal and having a fluorination rate of 55% or more was HCF ₂ CF ₂ OCH ₂ CF ₃ (1,1,2) ,
2-tetrafluoromethyl-2,2,2-trifluoroethyl ether: fluorination ratio 70%), ethylene carbonate (relative dielectric constant: 90) as an organic solvent having a relative dielectric constant of 10 or more, and acyclic carbonic acid. Using diethyl carbonate as an ester, these HCF ₂ CF ₂ OCH
_A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1, except that a mixed solvent of ₂ CF ₃ , ethylene carbonate and diethyl carbonate in a volume ratio of 60: 35: 5 was used as an electrolyte solvent. The obtained electrolyte was a homogeneous phase, and no separation of the electrolyte was observed.

Example 3 A non-cyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ group at the terminal and having a fluorination rate of 55% or more was HCF ₂ CF ₂ OCH ₂ CF ₃ (1,1,2) ,
Using 2-tetrafluoromethyl-2,2,2-trifluoroethyl ether: a fluorination ratio of 70%, triethyl phosphate (relative dielectric constant: 21) and vinylene carbonate (specific ratio) as an organic solvent having a relative dielectric constant of 10 or more. Dielectric constant: 13
0), the volume ratio of these HCF ₂ CF ₂ OCH ₂ CF ₃ , triethyl phosphate and vinylene carbonate is 6
A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1, except that a mixed solvent of 0:30:10 was used as an electrolyte solvent. The obtained electrolyte was a homogeneous phase, and no separation of the electrolyte was observed.

Example 4 A non-cyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ group at a terminal and having a fluorination rate of 55% or more is CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H (2
2,3,3,3-pentafluoropropyl-1,1,
2,2-tetrafluoroethyl ether: fluorination rate =
Using about 83%), the relative dielectric constant of 10 or more organic solvents as ethylene carbonate (dielectric constant: 90) was used, using diethyl carbonate as a non-cyclic carbonate, the _{CF 3 CF 2 CH 2 OCF 2} CF 2 The volume ratio of H, ethylene carbonate and diethyl carbonate is 80:
Except that a mixed solvent of 15: 5 was used as the electrolyte solvent,
A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1. The obtained electrolyte was a homogeneous phase, and no separation of the electrolyte was observed.

Example 5 A non-cyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ group at a terminal and having a fluorination rate of 55% or more was HCF ₂ CF ₂ CH ₂ OCHF ₂ (2, 2,
3,3-tetrafluoropropyl-difluoromethyl ether: fluorination rate = about 60%) and a relative dielectric constant of 10
As the above organic solvent, triethyl phosphate (dielectric constant: 2
Using 1) and vinylene carbonate (relative dielectric constant: 130) and using methyl ethyl carbonate as the acyclic carbonate, the volumes of these HCF ₂ CF ₂ CH ₂ OCHF ₂ , triethyl phosphate, vinylene carbonate and methyl ethyl carbonate are used. A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1, except that a mixed solvent having a ratio of 50: 20: 20: 10 was used as an electrolyte solvent. The obtained electrolyte was a homogeneous phase, and no separation of the electrolyte was observed.

Comparative Example 1 A non-cyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ terminal at a fluorination rate of 55% or more was replaced with a fluorinated hydrocarbon CF ₃ CHFCHFCF
₂ CF ₃ , and this CF ₃ CHFCHFCF ₂ CF ₃
Tried to prepare an electrolyte by dissolving 1.0 mol / l of LiPF _{6 in} a mixed solvent of 95: 5 by volume with ethylene carbonate, but the solvent was separated into two phases, and a uniform electrolyte was obtained. Could not get.

COMPARATIVE EXAMPLE 2 A non-cyclic fluorinated ether having at least one --CF ₂ H or --CFH ₂ group at the terminal and having a fluorination rate of 55% or more was replaced with a --CF ₂ H group or --CFH _{2 at the terminal.} CF ₃ CF ₂ C which is an acyclic fluorinated ether having no group
Using F ₂ OCH ₃ , the CF ₃ CF ₂ CF ₂ OCH ₃
Attempts to prepare an electrolyte by dissolving 1.0 mol / l of LiPF _{6 in} a mixed solvent of 80:20 by volume with ethylene carbonate, but the solvent is separated into two phases and a uniform electrolyte is obtained. Could not get.

Comparative Example 3 As a non-cyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ terminal at a fluorination rate of 55% or more, HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (1,
1,2,2-tetrafluoroethyl-2,2,3,3-
Tetrafluoropropyl ether: fluorination rate: about 67
%) And the HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂
H and ethylene carbonate were mixed at a volume ratio of 92: 8, and an attempt was made to prepare an electrolyte by dissolving 1.0 mol / l of LiPF _{6 in} this mixed solvent. However, the solvent was separated into two phases. And a uniform electrolytic solution could not be obtained.

Comparative Example 4 A cylindrical non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1, except that a mixture of ethylene carbonate and ethyl methyl carbonate at a volume ratio of 90:10 was used as an electrolyte solvent. Produced.

Comparative Example 5 As an acyclic fluorinated ether having at least one --CF ₂ H group or --CFH ₂ group at a terminal and having a fluorination rate of 55% or more, HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (1,
1,2,2-tetrafluoroethyl-2,2,3,3-
Tetrafluoropropyl ether: Fluorination rate about 67
%) And the HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂
A cylindrical non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that a mixed solvent of H and diethyl carbonate at a volume ratio of 70:30 was used as the electrolyte solvent.

The batteries of Examples 1 to 5 and Comparative Examples 4 to 5 (Comparative Examples 1 to 5 did not produce batteries because uniform electrolytes could not be obtained. And the battery characteristics were examined only for the batteries of Comparative Examples 4 and 5).
After charging and discharging in the range of V, each battery was charged at 2.75 V at 1 C.
The discharge capacity when the battery was discharged to the maximum was measured. The results are shown in Table 1. The discharge capacity of the battery of Comparative Example 4 under the above conditions was 10
It is indicated by an index when it is set to 0. Further, with respect to the batteries of Examples 1 to 5 and Comparative Example 4, the batteries were heated to a high temperature and the safety valve was operated [that is, in the battery shown in FIG. When gas is generated inside the battery and the internal pressure of the battery rises and reaches a predetermined pressure, the central portion of the explosion-proof valve 9 is deformed in the direction of the internal pressure (upward direction in FIG. 1) due to the increase of the internal pressure, Along with this, a shearing force acts on the thin portion 7a integrated at the welding portion 11, and the thin portion 7a is broken, or welding of the projecting portion 9a of the explosion-proof valve 9 and the thin portion 7a of the sealing plate 7 is performed. As a result, the sealing portion at the upper part of the battery is disassembled in advance, assuming that the portion 11 has peeled off, whereby the gas inside the battery has been discharged from the gas outlet 8a of the terminal plate 8 to the outside of the battery. With the inside exposed, Heating the pond to 100 ° C., close the fire exposed portion was examined whether flammable. Table 1 also shows the results.

[0052]

[Table 1]

As shown in Table 1, the batteries of Examples 1 to 5 had the same high capacity as the battery of Comparative Example 4, which was a conventional high capacity battery, and did not ignite in the flammability test.
Safety was high.

On the other hand, although the battery of Comparative Example 4 had a high capacity, it ignited in the flammability test, and was lacking in safety. The battery of Comparative Example 5 had a low capacity.
Since the battery of Comparative Example 5 had a low capacity as described above, the flammability test was not performed.

[0055]

As described above, according to the present invention, a non-aqueous electrolyte secondary battery having a high capacity, flame retardancy and high safety can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a non-aqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Electrolyte

Continued on the front page F-term (reference)

Claims (7)

[Claims] 1. A non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, and a non-aqueous solvent-based electrolyte containing a lithium salt, wherein the electrolyte has at least a -CF ₂ H group or a -CFH ₂ group at a terminal. 55% having at least one of
An organic solvent containing the above acyclic fluorinated ether and an organic solvent having a relative dielectric constant of 10 or more, wherein the content of the acyclic fluorinated ether in the electrolytic solution is 40 to 90% by volume and the relative dielectric constant is 10 or more. A nonaqueous electrolyte secondary battery having a solvent content of 5 to 50% by volume. 2. The method according to claim 1, wherein at least one of the organic groups adjacent to the ether oxygen of the acyclic fluorinated ether is — (CF ₂ ) _n
—CF ₂ H (n = 1 to 6) or —CH ₂ — (CF ₂ )
Non-aqueous electrolyte secondary battery according to claim 1 wherein the _{m -CF 2 H (m = 0~5} ). 3. The method according to claim 1, wherein the acyclic fluorinated ether is HCF ₂ C
F ₂ CH ₂ OCF ₂ CF ₂ H, HCF ₂ CF ₂ OCH ₂
CF ₃ , CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H, HCF
At least one non-aqueous electrolyte secondary battery of claim 1, wherein selected from the group consisting of ₂ CF ₂ CH ₂ OCHF _2. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the organic solvent having a relative dielectric constant of 10 or more is a cyclic carbonate and / or a phosphoric acid triester. 5. The lithium salt is LiPF ₆ , LiAs.
F _6, at least one inorganic lithium salt selected from the group consisting of LiBF ₄ and LiClO _4, any of claims 1 to 4 concentration of the lithium salt in the electrolyte is 0.5 to 2 mol / l A non-aqueous electrolyte secondary battery according to any of the above items. 6. The non-aqueous electrolyte secondary according to claim 1, wherein the negative electrode active material is a carbon-based material having an interplanar distance (d ₀₀₂ ) of the (002) plane of 0.34 nm or less. battery. 7. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrolyte contains an acyclic carbonate in an amount of 10% by volume or less.