JPH11214032A - Nonaqueous electrolytic solution and nonaqueous electrolytic solution battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte solution with superior battery performance and a nonaquepous electrolytic solution battery that restrains vaporization and resolution of the electrolyte solution and simultaneously reduces the possibility of breaking and firing the battery due to a generated gas. SOLUTION: This nonaqueous electrolyte solution battery is provided with a positive electrode, comprising an oxide or a sulfide that can be doped/dedoped with lithium ions, a negative electrode consisting of a carbon material that can be doped/dedoped with lithium metal, a lithium alloy, or lithium ions, and a nonaqueous electrolyte solution. The nonaqueous solution is a nonaqueous solution battery comprising a siloxane derivative shown by the formula and at least one kind of lithium metallic salt. In the formula, (a) represents an integer from 1 to 50, (b) represents an integer from 1 to 20, (m) represents an integer from 0 to 40, (n) represents from 0 to 40, R represents a hydrogen element or alkyl each of which can be substituted. However, when b>1, (b) number of Ds may be the same or different.

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 which improves safety during a short circuit by using a specific electrolyte and exhibits excellent battery performance even at a high voltage, and a non-aqueous electrolyte using the same. The present invention relates to a water electrolyte battery.

[0002]

2. Description of the Related Art In recent years, portable electronic products such as a camera-integrated video tape recorder, a portable telephone, and a laptop computer have been rapidly spreading. Also became an exhaust gas such as NO _x from the point of view of environmental protection as the development of electric vehicles that do not exhaust into the air is taken up as a social problem. Under such circumstances, research and development on a portable power supply and a battery as a clean energy source, particularly a secondary battery, are being actively promoted. Among them,
Lithium or lithium ion secondary batteries have attracted great expectations because they can obtain higher energy densities than lead batteries and nickel cadmium batteries, which are conventional aqueous electrolyte secondary batteries.

[0003] The electrolytic solution of the lithium or lithium-ion battery, ethylene carbonate low molecular, or propylene carbonate, carbonate ester nonaqueous solvent such as diethyl carbonate, to dissolve the lithium based electrolyte salt LiPF ₆ or the like as an electrolyte The liquid state is widely used because it has relatively high conductivity and is stable in potential.

[0004]

Although the above-mentioned nonaqueous electrolyte battery has high performance, it has a problem in safety because a flammable organic solvent is used as the electrolyte. For example, when a short circuit occurs, a large current suddenly flows into the battery and generates heat, thereby evaporating an electrolyte containing an organic solvent,
There was a problem of decomposing and generating gas. And
This gas generation could cause damage, rupture, or ignition of the battery. Heretofore, as a solution to these problems, there has been a method of providing a safety valve or a current cutoff device which is opened by a rise in battery internal pressure.

[0005] However, such a method of improving the structural mechanism cannot always solve any problem, and a fundamental method of improving the material of the battery is required to improve the safety performance of the battery. I have.

The present invention has been proposed to solve the above-described problems, and has as its object to provide a non-aqueous electrolyte having excellent chemical and thermochemical stability. Further, it is an object of the present invention to provide a non-aqueous electrolyte battery which suppresses vaporization and decomposition of the electrolyte, and at the same time reduces the risk of battery breakage and ignition due to gas generation, and has excellent battery performance.

[0007]

Means for Solving the Problems In order to solve the above-mentioned object, the present inventors have made intensive studies and as a result, as an electrolyte solution material, have high chemical stability, flame retardancy or low vapor pressure inorganic high inorganic material. It has been found that by using a siloxane derivative which is a molecule, vaporization and decomposition of the electrolytic solution can be suppressed, and at the same time, the risk of battery breakage and ignition can be reduced, and excellent battery performance can be obtained.

[0008] That is, the non-aqueous electrolyte according to the present invention is characterized by comprising a siloxane derivative represented by the following chemical formula 3 and at least one alkali metal salt.

[0009]

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The siloxane derivative preferably has a kinematic viscosity at a temperature of 25 ° C. of not more than 5000 cSt and an average molecular weight of not more than 10,000. By optimizing the kinematic viscosity and the average molecular weight, it becomes possible to synthesize a solvent having an appropriate viscosity that can be used as an electrolytic solution and a solubility suitable for mixing.

As described above, the non-aqueous electrolyte according to the present invention comprises:
The use of a siloxane derivative, which is an inorganic polymer with high chemical stability and flame retardancy or low vapor pressure, suppresses vaporization and decomposition of the electrolytic solution even in the event of a short circuit, resulting in the risk of battery damage and fire. And has excellent battery performance even at high voltages.

On the other hand, the non-aqueous electrolyte battery according to the present invention comprises a positive electrode made of an oxide or sulfide capable of doping / dedoping lithium ions, a lithium metal, a lithium alloy,
Or a negative electrode made of a carbon material capable of doping / dedoping lithium ions. The nonaqueous electrolyte battery according to the present invention includes a nonaqueous electrolyte comprising a siloxane derivative represented by the following Chemical Formula 4 and at least one lithium metal salt.

[0013]

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The siloxane derivative preferably has a kinematic viscosity at a temperature of 25 ° C. of not more than 5000 cSt and an average molecular weight of not more than 10,000. By optimizing the kinematic viscosity and the average molecular weight, it becomes possible to synthesize a solvent having an appropriate viscosity that can be used as an electrolytic solution and a solubility suitable for mixing.

As described above, the nonaqueous electrolyte battery according to the present invention uses a siloxane derivative, which is an inorganic polymer having high chemical stability, flame retardancy or low vapor pressure, as an electrolyte. It suppresses the vaporization and decomposition of the electrolyte even during a short circuit, reduces the risk of battery breakage and ignition, and has excellent battery performance even at high voltages.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a non-aqueous electrolyte according to the present invention and a non-aqueous electrolyte battery using the same will be described in detail.

The non-aqueous electrolyte according to the present invention is characterized by comprising a siloxane derivative represented by the following chemical formula (5) and at least one alkali metal salt.

[0018]

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The above-mentioned siloxane derivative is a chain-type siloxane derivative having a silicon-oxygen chain bond as a basic skeleton and a silicon-containing side chain, which is a monovalent organic group, having good chemical stability. It is an inorganic polymer that has high thermochemical stability due to its high flame retardancy or low vapor pressure.

Further, the siloxane derivative is required to have a structure in which the viscosity is relatively low and the alkali metal salt can be dissolved. That is, the siloxane derivative has a kinematic viscosity at a temperature of 25 ° C. of 5,000 cSt (centistokes) or less and an average molecular weight of 10,000.
It is required that:

Further, it is more preferable that the electrolyte has a conductivity at a temperature of 25 ° C. of 0.1 mS · cm ⁻¹ or more.

Proper viscosity to withstand use as an electrolyte,
Solubility suitable for mixing can be attained by appropriately selecting the side chain groups of D and D 'shown in Chemical Formula 5. Advantageously, the side chain group of D ′ shown in Chemical formula 5 contains an ether bond. A is 1 to 50, b is 1 to 20, and the sum of a and b is more preferably 1 to 40. In addition, hydrogen in D, D ', and the substituent R may be replaced by halogen elements, such as fluorine and boron.

On the other hand, as the alkali metal salt to be dissolved in the above-mentioned siloxane derivative, a salt of a light metal such as lithium, sodium or aluminum can be used, and it is convenient depending on the type of battery using the non-aqueous electrolyte. Can be determined.

For example, when forming a lithium or lithium ion secondary battery, LiBF ₄ , LiCl
O ₄ , LiPF ₆ , LiAsF ₆ , CF ₃ SO ₃ Li, (C
F ₃ SO ₂ ) ₂ NLi, C ₄ F ₉ SO ₃ Li, CF ₃ CO ₂ L
i, (CF ₃ CO ₂ ) ₂ NLi, C ₆ F ₅ SO ₃ Li, C ₈ F
₁₇ SO ₃ Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (C ₄ F ₉ S
O ₂ ) (CF ₃ SO ₂ ) NLi, (FSO ₂ C ₆ F ₄ ) (CF
_{3 SO 2) NLi, ((} CF 3) 2 CHOSO 2) 2 NLi,
(CF ₃ SO ₂ ) ₃ CLi, (C ₆ F ₃ (CF ₃ ) _2-3 ,
5) ₄ BLi, may be used lithium salts such as LiCF _3, LiAlCl _4.

As described above, the non-aqueous electrolyte containing the siloxane derivative and the alkali metal salt described above uses the siloxane derivative having excellent chemical stability and thermochemical stability as a solvent. Even when a large current flows, vaporization and decomposition of the electrolytic solution are suppressed.
Therefore, the non-aqueous electrolyte battery using this non-aqueous electrolyte reduces the risk of rapid damage or ignition of the battery during a short circuit, improves safety, and has excellent battery performance even at high voltages. Can be demonstrated.

As described above, the above-mentioned non-aqueous electrolyte is composed of a positive electrode made of an oxide or sulfide capable of doping and undoping lithium, and a carbonaceous material capable of doping and undoping lithium metal, a lithium alloy or lithium ions. It is suitable for use as an electrolyte of a non-aqueous electrolyte secondary battery provided with a negative electrode comprising:

For example, when forming a lithium secondary battery, TiS ₂ , MoS ₂ , NbSe may be used as the positive electrode active material.
₂ , a metal sulfide or oxide not containing lithium, such as V ₂ O ₅ , or a lithium composite oxide containing lithium can be used.

In particular, in order to form a battery having a high energy density, Li _x MO ₂ (where M is preferably one or more transition metals, and 0.05 ≦ x ≦ 1.10.) Is preferably used. As the lithium composite oxide, specifically, Li
CoO ₂ , LiNiO ₂ , Li _x Ni _y Co _1-y O ₂ (wherein,
x and y vary depending on the discharge state of the battery, and usually 0 <x <
1, 0.7 <y ≦ 1. ), LiMn ₂ O _{4 and the} like.

Such a lithium composite oxide comprises lithium carbonate, nitrate, oxide or hydroxide, and carbonate, nitrate, oxide or hydroxide such as cobalt, manganese or nickel. It can be adjusted by pulverizing and mixing according to a desired composition and firing in an oxygen atmosphere in a temperature range of 600 to 1000 ° C.

As the negative electrode, lithium, Li-A
For example, a lithium alloy such as a 1 alloy, or a carbon material capable of doping / dedoping lithium ions can be used. As the carbon material, a material adjusted at a predetermined temperature and atmosphere is used. Examples of this raw material include pyrolytic carbons, cokes (petroleum coke, pitch coke, etc.), artificial graphites, natural graphites, carbon black (acetylene black, etc.), glassy carbons, and organic polymer material fired bodies. (Organic polymer material fired at an appropriate temperature of 500 ° C. or higher in an inert gas stream or in a vacuum) or carbon fiber can be used.

As the solvent for the non-aqueous electrolyte, one of the above-mentioned siloxane derivatives may be used alone, or may be used in combination with other conventionally known solvents. As other solvents, for example, propylene carbonate, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane,
1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, dipropylcarbonate, diethylether, sulfolane, methylsulfolane, acetonitrile, propylnitrile, anisole, acetate, propionate, 2-methyltetrahydrofuran And the like may be used, and two or more kinds may be mixed and used.

As a separator for preventing a current short circuit or the like due to the above-mentioned contact between the positive electrode and the negative electrode, a material that can surely prevent the contact between the two electrodes and that can pass or contain an electrolytic solution. For example, a nonwoven fabric, a porous ceramic film, a porous thin film, or the like made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene can be used.

As described above, in a non-aqueous electrolyte battery using an inorganic polymer siloxane derivative having high chemical stability, flame retardancy, or low vapor pressure as the electrolyte, vaporization and decomposition of the electrolyte are performed. At the same time, the risk of ignition and ignition is reduced, and the battery performance is excellent even at a high voltage.

As other components of the battery of the present invention, those commonly used can be used without any problem. In addition, the form of the battery is not particularly limited, and the form of the battery is not limited, such as a coin type, a button type, a paper type, a square type or a spiral type cylindrical battery.

[0035]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A siloxane derivative (1) represented by the following chemical formulas (6) to (8)
To (3) were added at different lithium salt concentrations. These are sandwiched between stainless steel plates each having a thickness of 0.145 cm and an area of 0.7854 cm ² , and a so-called Cole-Cole plot in which the applied sine wave AC voltage is expressed in a symbolic method (complex representation). The conductivity was determined. Table 1 shows the results.

The kinematic viscosity at 25 ° C. is given by
The siloxane derivative (1) represented by the formula is 100 cSt, and the siloxane derivative (2) represented by the formula (7) is 1600 cS
t, the siloxane derivative (3) represented by Formula 8 is 400 c
St.

[0038]

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[0039]

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[0040]

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[0041]

[Table 1]

From the results shown in Table 1, it can be seen that all of the siloxane derivatives represented by Chemical Formulas 6 to 8 have conductivity that can be used for batteries. Further, it can be seen that among the siloxane derivatives (1) to (3) having different kinematic viscosities, higher conductivity can be obtained by using the siloxane derivative (1) having a lower kinematic viscosity.

Example 2 A siloxane derivative (1) represented by the above formulas (6) and (7)
The oxidative stability was examined by measuring the cyclic voltammogram of (2). For the measurement, an electrochemical cell made of three electrodes was used, and a nickel electrode (diameter: 0.5 mm) was used as a working electrode, and lithium metal was used as a counter electrode and a reference electrode. And 100
The potential until the oxidation current of μA · cm ⁻² was generated was set to a stable potential range. As a result, the stable oxidation potential of Sample 2 was 5.8 V, and the stable oxidation potential of Sample 6 was 6.0.
V.

From these results, it is understood that the siloxane derivative can exhibit excellent battery performance even at a high voltage.

Example 3 A coin cell using LiCoO _{2 for} the positive electrode, a carbon material for the negative electrode, and the siloxane derivative (1) shown in Chemical formula 6 for the electrolyte was prepared, and a charge / discharge test was performed. Upper limit voltage: 4.2V,
Lower limit voltage: 3.0 V, discharge current: 100 μA, 2
The charge / discharge was repeated until 0 cycle. FIG. 1 shows the charge / discharge test at that time.

From the results shown in FIG. 1, the siloxane derivative (1)
Indicates that the battery has excellent battery performance.

[0047]

As is clear from the above description, according to the present invention, since a specific siloxane derivative is used as an electrolytic solution, a non-aqueous electrolytic solution having excellent chemical and thermochemical stability. And a nonaqueous electrolyte battery having excellent safety and excellent battery performance even at a high voltage can be obtained.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a charge / discharge curve of a nonaqueous electrolyte battery according to an embodiment.

Claims (9)

[Claims] 1. A non-aqueous electrolyte comprising a siloxane derivative represented by the following chemical formula 1 and at least one alkali metal salt. Embedded image 2. The non-aqueous electrolyte according to claim 1, wherein the siloxane derivative has a kinematic viscosity at a temperature of 25 ° C. of 5,000 cSt or less. 3. The non-aqueous electrolyte according to claim 1, wherein the siloxane derivative has an average molecular weight of 10,000 or less. 4. The non-aqueous electrolyte according to claim 1, wherein the alkali metal salt is a lithium metal salt. 5. The conductivity at a temperature of 25 ° C. is 0.1 mS.
The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte is not less than cm ^-1 . 6. A positive electrode made of an oxide or sulfide capable of doping and undoping lithium ions, and a positive electrode made of lithium metal, a lithium alloy, or lithium ions.
In a non-aqueous electrolyte battery including a negative electrode made of a undoped carbon material and a non-aqueous electrolyte, the non-aqueous electrolyte comprises a siloxane derivative represented by the following chemical formula 2, and at least one lithium metal A non-aqueous electrolyte battery comprising a salt. Embedded image 7. The nonaqueous electrolyte battery according to claim 6, wherein the siloxane derivative has a kinematic viscosity at a temperature of 25 ° C. of not more than 5000 cSt. 8. The non-aqueous electrolyte battery according to claim 6, wherein the siloxane derivative has an average molecular weight of 10,000 or less. 9. The non-aqueous electrolyte battery according to claim 6, wherein the non-aqueous electrolyte has a conductivity at a temperature of 25 ° C. of 0.1 mS · cm ⁻¹ or more.