JPH10334730A - Organic electrolyte and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable, high-performance, inexpensive electrolyte minimized in impurity and easy to manufacture and handle to provide a long-lived, highly reliable, and high-performance nonaqueous battery by adding an alumina fine particle having a high specific surface area of a specified value or more and a low water content of a specified value or less to an organic electrolyte. SOLUTION: This organic electrolyte comprises at least one each of alumina fine particles, organic solvents and electrolytic salts. The alumina particle has a BET specific surface area of 10 m<2> /g or more, a maximum diameter of 5 μm or less, and a water content (Karl Fischer titration value) of 3000 ppm or loess, and its addition amount is set to 0.05-30 wt.% of the whole electrolyte. The electrolyte preferably has a viscosity of 2000 cPs (shear rate of 20-400 s<-1> ) or less at room temperature, a moisture value of 200 ppm or less, and a free acid quantity (neutralization titration value) of 100 ppm or less. An organic solvent is formed of cyclic and/or chain carbonates, and the electrolyte is preferably formed of an alkali metal salt, quaternary ammonium salt, or transition metal salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic electrolyte containing alumina-based fine particles having a high specific surface area and a low water content, and a battery using the organic electrolyte.

[0002]

2. Description of the Related Art Among small batteries, lithium primary batteries and lithium (ion) secondary batteries have recently been rapidly mounted on small portable devices due to their high energy density, and have shown rapid growth. For example, LiCoO ₂ , LiNiO
_2, LiMnO _2, MoS metal oxides such as _2, with a metal sulfide in the positive electrode, lithium, lithium alloy, a lithium secondary battery using a carbon material or an inorganic compound with lithium ion can occluding and releasing the negative electrode is much studied ing. "Journal of the Electrochemical Society (J. E
138 (No. 3), 665.
1991, a battery using MnO ₂ or NiO ₂ as a positive electrode is reported. Important components other than the positive and negative electrodes of these lithium primary batteries and lithium (ion) secondary batteries include organic electrolytes and separators.

[0003] A porous film such as a polyolefin nonwoven fabric or a polyolefin microporous film is used as a separator. The function of the separator is to electrically isolate the positive electrode and the negative electrode so that they do not short-circuit,
It is required not to hinder the movement of ions in the organic electrolyte interposed between the negative electrodes. In addition, it is preferable that the battery has the above-described function, as thin as possible because the energy density of the whole battery is increased. To provide these functions, a porous thin film is currently used as a separator.

The organic electrolyte is LiPF ₆ , LiBF ₄ , L
Fluorine-based lithium salts such as iAsF ₆ and LiCF ₃ SO ₃ are dissolved in various organic solvents, and are used after being dehydrated and purified to have a water content of 30 ppm or less and other inorganic impurities of 1 ppm or less. Examples of the organic solvent used in the organic electrolyte include propylene carbonate (PC), ethylene carbonate (EC), and γ-butyl lactone (γ) having high dielectric constant and high viscosity.
-BL) and low-viscosity chain carbonates such as dimethyl carbonate (DMC) and diethyl carbonate (DEC);
2-dimethoxyethane (DME), diglyme (D
A mixed solvent such as G) and ethers such as dioxolan (DOX) is used. In particular, Li + batteries recently launched on the market and expected to grow significantly as high energy density secondary batteries include EC + DEC or EC +
A DMC mixed solvent is mainly used because it has excellent stability to a graphite-based negative electrode and a metal oxide-based positive electrode, and has a high decomposition voltage. However, EC is a solid at room temperature and therefore has a problem in low-temperature characteristics. DEC and DMC have a high vapor pressure, and thus have problems in the battery manufacturing process and high-temperature characteristics. PC has a wide operating temperature range.
There is a problem that it cannot be used alone because it has high reactivity with the negative electrode.

As an electrolyte salt, a lithium salt having a fluorine-based anion is preferably used because it has a high degree of dissociation in an organic solvent, has a high ionic conductivity, and has good electrochemical stability. LiPF ₆
Is particularly excellent in characteristics. However, these fluorine-based lithium salts generate HF and its derivatives which are strong acids at the time of synthesis, remain, and release them as impurities into the electrolytic solution. It is unstable to heat and water and decomposes to produce HF and its derivatives. HF and its derivatives react with Li and carbon material anodes and oxide cathodes to generate LiF coatings and hydrogen gas, not only causing battery deterioration, but also organic polymers such as other solvents and sealing materials. Deteriorates materials and corrodes metal materials such as battery cans. Therefore, the trader pays a great deal of effort on prevention of HF generation during the production of the electrolyte, storage method after preparation, and the like.

On the other hand, since these electrolytes have fluidity and volatility, when applied as a battery, there are problems such as liquid leakage and liquid leakage. In order to improve the property, the polymerization or gelation of the electrolytic solution has been actively carried out recently, but there is still no ionic conductivity or the like exceeding the electrolytic solution. Japanese Patent Application Laid-Open No. 3-98263 discloses a problem of the electrolytic solution by adding a large amount of a powdery inert, non-conductive solid such as silica, alumina, or titania to an organic electrolytic solution to eliminate fluidity. Attempts have been made to solve the problem, but no study has been made on the removal of impurities such as moisture in the electrolytic solution. In March 1997, the Electrochemical Society of Japan Spring Meeting (Kanagawa University) 1A21 reported physical properties when a large amount of α-alumina was added to a LiClO ₄ -based organic electrolyte.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stable, high-performance, and low-cost organic electrolyte solution for an electrochemical device, which has a small amount of impurities, is easy to manufacture and handle. Another object of the present invention is to obtain a high-performance non-aqueous battery having a long life and excellent reliability.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above problems, and as a result, by adding specific alumina fine particles having a high specific surface area and a low water content to an organic electrolytic solution, impurities in the electrolytic solution have been obtained. And improved stability. Further, they have found that impurities in an electrochemical element using the electrolytic solution can also be adsorbed. In addition, they have found that the cation mobility in the electrolytic solution can be improved particularly by the interaction between the alumina surface and the anion.

That is, the present invention provides (1) an organic electrolytic solution containing at least one kind of alumina fine particles, at least one kind of organic solvent, and at least one kind of electrolyte salt, wherein the alumina type fine particles have a BET specific surface area of 1
An organic electrolyte having 0 m ² / g or more, a maximum diameter of 5 μm or less, a water content (Karl Fischer titration value) of 3000 ppm or less, and an addition amount of 0.05 to 30 wt% of the whole electrolyte. (2) At room temperature, the viscosity of the electrolytic solution is 2000 cps or less (shear speed: 20 to 400 s ^-1 ), the moisture value of the electrolytic solution (Karl Fischer titration value) is 200 ppm or less, and the free acid amount of the electrolytic solution (neutralization titration value). ) Is 100 ppm or less.

(3) 600 to 12 alumina-based fine particles
The organic electrolyte according to the above (1) or (2), which is γ-alumina heat-treated at 00 ° C. (4) The organic electrolytic solution as described in (1) or (2) above, wherein the alumina-based fine particles are an alkali metal / aluminum composite oxide heat-treated at 600 to 1200 ° C. (5) The alumina-based fine particles are aggregates of primary particles having a crystal particle diameter of 0.1 μm or less, and the size of the aggregates is 0.1 μm.
(1) to (5) above, wherein
The organic electrolytic solution according to any one of (4).

(6) The above-mentioned (1) to (1), wherein the electrolyte salt is at least one selected from alkali metal salts, quaternary ammonium salts, quaternary phosphonium salts, and transition metal salts.
The organic electrolytic solution according to any one of (5). (7) At least one electrolyte salt is LiPF ₆ and / or
Or LiBF ₄ and / or LiN (CF ₃ SO ₂ )
_2. The organic electrolytic solution according to the above (6), which is ₂ . (8) The above (1), wherein the at least one organic solvent is a cyclic and / or chain carbonate.
The organic electrolytic solution according to any one of (1) to (7).

(9) A battery using at least one kind of the organic electrolyte described in (1) to (8). (10) Lithium, lithium alloy,
Alternatively, the lithium secondary battery according to the above (9), wherein at least one material selected from a carbon material capable of inserting and extracting lithium ions, an inorganic oxide and an inorganic chalcogenide is used. (11) The lithium secondary battery according to (10), wherein a material composed of a conductive polymer, a metal oxide, a metal sulfide, and / or a carbon material is used as the positive electrode active material.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. [1] Organic Electrolyte Solution The organic electrolyte solution of the present invention contains at least one kind of alumina-based fine particles, at least one kind of organic solvent, and at least one kind of electrolyte salt. Hereinafter, each component will be described. (1-a) Organic Solvent As the organic solvent used in the organic electrolytic solution of the present invention, those having high solubility of the electrolyte salt and not adversely affecting the electrochemical element to be used are preferable. That is, a compound having a large dielectric constant and a wide electrochemical stability range is suitable. Such solvents include cyclic and / or chain carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, bismethoxyethyl carbonate, ethylmethoxyethyl carbonate, tetrahydrofuran,
Cyclic and / or chain ethers such as dioxolane and 1,2-dimethoxyethane; oligoethers such as triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; lactones such as γ-butyl lactone; acetonitrile, benzonitrile and tolunitrile And nitrogen-containing compounds such as dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, and N-vinylpyrrolidone; sulfur compounds such as sulfolane; and phosphoric acid esters. Among them, carbonates, ethers,
Oligoethers and lactones are preferred, and carbonates are particularly preferred.

(1-b) Electrolyte salt The composite ratio of the electrolyte salt used in the organic electrolyte of the present invention is preferably from 1 to 50% by weight, particularly preferably from 5 to 30% by weight, based on the weight of the solvent. If the electrolyte salt used in the composite is present at a ratio of 50% by weight or more, it is difficult to dissolve, the viscosity increases, and the movement of ions is greatly inhibited.
At the following ratio, the absolute amount of ions becomes insufficient and the ionic conductivity decreases.

The type of electrolyte salt used for the composite is not particularly limited, and an electrolyte salt containing ions to be used as a carrier in an electrochemical element such as a battery may be used. Desirably large, Li
CF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiPF
₆ , LiClO ₄ , LiI, LiBF ₄ , LiSCN,
LiAsF ₆ , NaCF ₃ SO ₃ , NaPF ₆ , NaC
10 ₄ , NaI, NaBF ₄ , NaAsF ₆ , KCF ₃
Alkali metal salts such as SO ₃ , KPF ₆ and KI;
₃ ) ₄ Quaternary ammonium salts such as ₄ NBF ₄ , (CH ₃ ) ₄
Quaternary phosphonium salts such as PBF ₄ and transition metal salts such as AgClO ₄ are recommended.

As the negative electrode active material used in the battery of the present invention, an alkali metal, an alkali metal alloy,
By using a material having a low oxidation-reduction potential using an alkali metal ion such as a carbon material as a carrier, a high voltage,
This is preferable because a high-capacity battery can be obtained. Therefore, when such a negative electrode is used in a battery using an alkali metal ion as a carrier, an alkali metal salt is required as an electrolyte in the solid polymer electrolyte. Examples of the kind of the alkali metal salt include LiCF ₃ SO ₃ , LiPF ₆ ,
LiClO ₄ , LiBF ₄ , LiSCN, LiAsF
₆ , LiN (CF ₃ SO ₂ ) ₂ , NaCF ₃ SO ₃ , L
iI, NaPF ₆ , NaClO ₄ , NaI, NaBF
₄ , NaAsF ₆ , KCF ₃ SO ₃ , KPF ₆ , KI and the like. Among the negative electrodes, the use of lithium or a lithium alloy as the alkali metal is most preferable in terms of high voltage and high capacity. Therefore, a lithium salt is also used as the electrolyte salt. Among them, LiPF ₆ ,
LiCF ₃ SO ₃ , LiBF ₄ , LiAsF ₆ , LiN
Those containing a fluorine-based anion such as (CF ₃ SO ₂ ) ₂ are preferable in terms of high degree of dissociation, high ionic conductivity, and a wide electrochemical stability region, and LiPF ₆ is particularly preferable.

(1-c) Alumina-based fine particles The organic electrolytic solution of the present invention is characterized in that alumina-based fine particles are added. The surface of the alumina-based fine particles has particularly high affinity for anions in the electrolytic solution, and has high ionic conductivity,
In particular, since the mobility of cations can be improved by reducing the binding of cations, it is preferable to use the cations in a state where the specific surface area is as high as possible and water adsorbed on the surface is removed. In addition, by adding alumina-based fine particles having a high specific surface area and a high surface activity with reduced adsorbed water, not only in the electrolytic solution but also in impurities in the electrochemical element, particularly in non-aqueous systems such as lithium batteries. When used, water and free acid can be adsorbed very well, and a great effect can be exhibited in reducing deterioration of the sealing material and other battery materials, and as a result, the life of the battery can be improved.

Among the inorganic fine particles, alumina-based fine particles have lower reactivity with lithium, higher interaction with anions, lower catalytic activity, and better electrochemical stability than silica, titania, magnesia and the like. And is non-electron conductive, so that it is most suitable as fine particles to be added to the organic electrolyte solution of the present invention.

Since the surface of the alumina-based fine particles has a particularly high affinity for the fluorine-based compound, the fluorine-based anion used in a Li-ion battery such as LiPF ₆ is specifically adsorbed on the surface of the alumina-based fine particles, and thus the lithium-based particles are lithium ion. The cations move easily, and as a result, the cation transport number in the system can be improved, and the current characteristics of the battery can be improved.
Li batteries such as Li ion batteries have a high degree of dissociation and high ion conductivity, such as LiPF ₆ , LiBF ₄ , L
Fluorinated electrolyte salts such as iN (CF ₃ SO ₃ ) ₂ are preferably used, but they are easily decomposed in the electrolytic solution.
A large amount of HF is released as a free acid, deteriorating electrodes, electrolytes, various polymers, and metals. On the other hand, in the organic electrolytic solution to which the alumina-based fine particles of the present invention are added, HF is hardly detected, and the life of other battery constituent materials is improved.

Specific examples of the alumina-based fine particles of the present invention include α, β, and α obtained by various production methods such as a solid phase method and a gas phase method.
Examples include γ-type Al ₂ O ₃ fine particles and alumina-based composite oxide fine particles such as LiAlO _{2 obtained} by reacting these with various inorganic substances such as Li salts. Among them, γ-type Al ₂ O such as aluminum oxide-C (trade name, manufactured by Degussa Co., Ltd.) and UA-5805 manufactured by Showa Denko Co., Ltd.
₃ Fine particles and LiAlO ₂ are suitable for the organic electrolyte of the present invention.

The ionic conductivity of the electrolyte, increasing the ion mobility, further the purpose of performing the adsorption of impurities, it is preferable specific surface area of the alumina particles is as large as possible, not less than 10 m ² / g by the BET method And preferably 50 m ² / g or more. Also, the size is preferably smaller, 5 μm or less, preferably 1 μm.
Below, more preferably, those having a size of 0.1 μm or less are used. In addition, various shapes such as a sphere, an egg, a cube, a rectangular parallelepiped, a cylinder or a rod can be used. However, from the viewpoints of the efficiency of removing impurities from the electrolyte, the ion conductivity, and the like, the alumina-based fine particles preferably have a secondary particle structure in which crystal particles are aggregated. Is 0.01 μm to 5
μm is particularly preferred.

If the amount of the alumina-based fine particles is too large, there arises a problem that the viscosity of the organic electrolytic solution is increased and the ionic conductivity is lowered. Therefore, the preferable addition amount is 0.05 to 30 wt% or less, particularly preferably 0.5 to 20 wt% based on the organic electrolyte.

The alumina-based fine particles of the present invention are preferably heat-treated before being added to the organic electrolyte. By heat treatment, water adsorbed on the surface of alumina-based particles is reduced,
In addition to suppressing free moisture diffusing into other materials, it is also possible to adsorb impurities of other materials and to improve stability in the system. In addition, moderate heat treatment causes partial sintering, which is also effective in forming secondary particles. The temperature and time of the heat treatment vary depending on the shape and type of the alumina-based fine particles to be used, but may be performed in the range of 200 to 1200 ° C. for about 2 to 300 hours, and the temperature is 600 to
A range of 1200 ° C. is particularly preferred. The heat treatment temperature is preferably as high as possible. However, if it exceeds 1200 ° C., sintering of the alumina-based fine particles proceeds and the activity of the surface is lowered, which is not preferable. The atmosphere during the heat treatment is not particularly limited to reduced pressure, in air, or in an inert atmosphere. However, after the heat treatment, it is necessary to handle in an atmosphere having a dew point of −30 ° C. or less to prevent re-adsorption of moisture. Particularly preferred is -50 ° C or lower. When the water content of the alumina-based fine particles thus heat-treated was determined by the Karl Fischer method,
It must be below 0 ppm.

(1-d) Water content of electrolyte solution, etc.
When the water content of the organic electrolytic solution of the present invention is 200 ppm or less (Karl Fischer titration value) and the free acid content is 100 ppm or less (neutralization titration value), preferably the water content is 50 ppm or less (Karl Fischer titration value). Acid amount is 30pp
m (neutralization titration value) or less, and can be used as an electrolyte suitable for non-aqueous batteries such as Li-ion batteries.

Further, the viscosity of the organic electrolytic solution to which the alumina-based fine particles of the present invention are added is adjusted to be low. Other components of the electrochemical element are generally porous and microporous, such as electrodes and separators, in order to efficiently perform the electrochemical reaction.If the viscosity of the electrolyte is too high, It is difficult to impregnate and composite them, which is not preferable.
In addition, the mobility of ions generally tends to decrease. Therefore, the viscosity of the organic electrolyte of the present invention is 20 at room temperature.
00 cps or less (shear speed with a rotational viscometer is 20 to 40)
^{0 s −1} ) is preferable, 1000 cps or less is more preferable, and 500 cps or less is more preferable.

[2] Battery When the organic electrolyte of the present invention is applied to a battery, the organic electrolyte contains a small amount of impurities and has a fast ion transfer, and thus has a long cycle life, a large take-out current, safety and reliability. , A battery with a high value is obtained. In addition, since the alumina fine particles have a high ability to adsorb impurities, the atmosphere and the process management during the production of the electrolytic solution and the electrochemical element are simplified, which is advantageous in terms of cost. The battery of the present invention can be manufactured by a known method except that the organic electrolytic solution of the present invention is used as the electrolytic solution. The components will be described below. (2-a) Negative Electrode The battery of the present invention uses lithium, a lithium alloy, a carbon material, a conductive polymer, and a low oxidation-reduction potential using an alkali metal ion such as a metal oxide or a metal chalcogenide as a carrier. It is preferable because a battery with high voltage and high capacity can be obtained. Among such negative electrode active materials,
Lithium metal or lithium alloys such as lithium / aluminum alloy, lithium / lead alloy and lithium / antimony alloy are particularly preferable because they have the lowest oxidation-reduction potential. In addition, the carbon material is particularly preferable because it has a low oxidation-reduction potential when occluding Li ions, and is stable and safe. Examples of carbon materials capable of inserting and extracting Li ions include natural graphite, artificial graphite, vapor-grown graphite, petroleum coke, coal coke, pitch-based carbon, polyacene, C ₆₀ ,
Fullerenes such as C ₇₀ and the like.

(2-b) Positive Electrode In the structure of the battery of the present invention, the positive electrode has a high oxidation-reduction potential electrode active material such as metal oxide, metal sulfide, conductive polymer or carbon material (positive electrode active material). Is preferable because a high-voltage, high-capacity battery can be obtained. Among such electrode active materials, metal oxides such as cobalt oxide, manganese oxide, vanadium oxide, nickel oxide, molybdenum oxide, molybdenum sulfide, and sulfide Titanium,
Metal sulfides such as vanadium sulfide are preferable, and manganese oxide, nickel oxide, cobalt oxide and the like are particularly preferable in terms of high capacity and high voltage.

In this case, the method for producing the metal oxide or metal sulfide is not particularly limited.
2, pp. 574, 1954 "by a general electrolytic method or a heating method. When these are used in a lithium battery as an electrode active material, for example, Li _x CoO ₂ or Li _x
It is preferable to use a state in which the Li element is inserted (composite) into the metal oxide or metal sulfide in the form of _x MnO ₂ or the like.
The method of inserting the Li element in this way is not particularly limited,
For example, the method of electrochemically inserting Li ions or the method described in U.S. Pat.
It can be carried out by mixing a salt such as i ₂ CO ₃ and a metal oxide and performing a heat treatment.

Also, in terms of being flexible and easy to form a thin film,
Conductive polymers are preferred. Examples of conductive polymers include:
Polyaniline, polyacetylene and its derivatives, polyparaphenylene and its derivatives, polypyrrole and its derivatives, polythienylene and its derivatives, polypyridinediyl and its derivatives, polyisothianaphthenylene and its derivatives, polyfurylene and its derivatives, polyselenophene and its Derivatives, polyarylenevinylenes such as polyparaphenylenevinylene, polythienylenevinylene, polyfurylenevinylene, polynaphthenylenevinylene, polyselenophenvinylene, polypyridinediylvinylene, and derivatives thereof, and the like. Among them, a polymer of an aniline derivative soluble in an organic solvent is particularly preferable. Also,
Carbon materials include natural graphite, artificial graphite, vapor-phase graphite,
Examples include petroleum coke, coal coke, graphite fluoride, pitch-based carbon, polyacene, and the like.

(2-c) Current Collector The current collector is preferably made of a material having electron conductivity, electrochemical corrosion resistance, and as large a specific surface area as possible.
For example, various metals and their sintered bodies, electron conductive polymers,
A carbon sheet and the like can be mentioned.

[0031]

The organic electrolyte of the present invention comprises an electrolyte salt, an organic solvent,
It contains alumina-based fine particles, has high ionic conductivity and good cation mobility, and can improve current characteristics and cycle characteristics of various electrochemical devices such as batteries. Furthermore, the organic electrolyte solution of the present invention has a high surface activity at a low moisture content after being heat-treated, and the addition of alumina-based fine particles having a high specific surface area has a small amount of impurities, and has a high ability to adsorb impurities of other materials. It is excellent in stability and can improve the life of electrochemical devices such as batteries. Further, in the present invention, by using the organic electrolytic solution, a battery having a long life, a large take-out current, a safe, reliable, and excellent workability can be obtained. Further, since the organic electrolytic solution of the present invention is non-aqueous, it can be combined with a negative electrode having a low oxidation-reduction potential and / or a positive electrode having a high oxidation-reduction potential. A secondary battery is obtained.

[0032]

The present invention will be described more specifically with reference to representative examples. These are merely examples for explanation, and the present invention is not limited to these.

Example 1 <Heat treatment of alumina-based fine particles> High-purity γ-alumina UA5805 manufactured by Showa Denko (crystal particle size 0.03 μm, average secondary particle size 1.8 μm, BET specific surface area 80 m ² / g) was applied to the atmosphere. After heating at 1000 ° C. for 5 hours in a medium and electric furnace, it was placed in an argon atmosphere glove box having a dew point of −60 ° C. in a high temperature state, and air-cooled to room temperature. When the water content of the UA5805 was measured with a Karl Fischer moisture meter,
It was 600 ppm. Further, the BET specific surface area after the heat treatment was 75 m ² / g, indicating that some sintering had occurred.

Example 2 Heat treatment U prepared in Example 1
A58050.33 g, diethyl carbonate (DEC) 4.
0 g, ethylene carbonate (EC) 2.0 g, LiPF
₆ (Hashimoto Chemical Battery Grade) 0.60 g was mixed well at room temperature in an argon atmosphere to prepare an electrolytic solution. The water content (Karl Fischer method) of this electrolyte is 20 ppm,
The free acid (in terms of HF) was 20 ppm or less (neutralization titration method). The ionic conductivity at 25 ° C. and −10 ° C. of the electrolytic solution was measured by an impedance method, and was 6.
It was 0 × 10 ⁻³ and 1.5 × 10 ⁻³ S / cm. The viscosity measured by a rotational viscometer at room temperature (25 ° C.) is 40 cps (380
s ^-1 ).

[Example 3] <Heat treatment of alumina-based fine particles> Aluminum oxide C manufactured by Nippon Aerosil (crystal particle size 0.013 µm, average secondary particle size about 0.1 µm (SEM observation), BET specific surface area 100 m ² / g) Was heated in an electric furnace at 1000 ° C. for 5 hours in the air, and then put in a high-temperature argon atmosphere glove box having a dew point of −60 ° C., and air-cooled to room temperature. The water content of the aluminum oxide C was measured by a Karl Fischer moisture meter and found to be 700 ppm.
In addition, the BET specific surface area after the heat treatment was 85 m ² / g, indicating that some sintering had occurred.

Example 4 UA as alumina-based fine particles
An organic electrolyte solution was prepared in the same manner as in Example 2 except that 0.33 g of the aluminum oxide C heat-treated in Example 3 was added instead of 5805. The water content (Karl Fischer method) of this electrolytic solution was 15 ppm. Free acid (HF
(Converted) was 20 ppm or less (neutralization titration method). The ionic conductivity of this electrolyte at 25 ° C. and −10 ° C. was measured by an impedance method, and was 6.4 × 10 ⁻³ and 1.6, respectively.
× 10 ^-3 S / cm. The viscosity measured by a rotational viscometer at room temperature (25 ° C.) was 48 cps (380 s ⁻¹ ).

Example 5 Example 4 was repeated except that 0.50 g of battery grade LiBF ₄ manufactured by Hashimoto Kasei was used instead of LiPF _6.
In the same manner as in the above, an organic electrolytic solution was obtained. The water content (Karl Fischer method) of this electrolytic solution was 25 ppm. The free acid (in terms of HF) was 20 ppm or less (neutralization titration method).
The ionic conductivity of this electrolyte at 25 ° C. and −10 ° C. was measured by an impedance method.
^-3 , 0.8 × 10 ^-3 S / cm. The viscosity measured with a rotational viscometer was 43 cps (380 s ^-1 ) at room temperature (25 ° C.).

Example 6 0.33 g of the heat-treated aluminum oxide C prepared in Example 3, 3.0 g of propylene carbonate (PC), γ-butyl lactone (γ-BL)
3.00 g and purified tetraethylammonium tetrafluoroborate (TEAB) 0.80 g manufactured by Hashimoto Kasei were mixed well at room temperature in an argon atmosphere to prepare an electrolyte solution. The water content (Karl Fischer method) of this electrolytic solution was 70 ppm. The free acid (in terms of HF) was 20 ppm or less (neutralization titration method). The ionic conductivity of this electrolyte at 25 ° C. and −10 ° C. was measured by an impedance method, and was found to be 12.0 × 10 ⁻³ and 3.0 × 10 ⁻³ S / cm, respectively. The viscosity measured by a rotational viscometer at room temperature (25 ° C.) is 120 cps (3
80 s ^-1 ).

[Example 7] <Heat treatment of alumina-based fine particles> High-purity γ-alumina UA5605 manufactured by Showa Denko (crystal particle size: 0.05 µm, average secondary particle size: 1.8 µm, BET specific surface area: 60 m ² / g) was applied to the atmosphere. After heating at 700 ° C. for 5 hours in a medium and electric furnace, it was placed in an argon atmosphere glove box having a dew point of −60 ° C. in a high temperature state, and air-cooled to room temperature. When the water content of the UA5605 was measured with a Karl Fischer moisture meter, it was 6%.
It was 00 ppm. There was no change in the BET specific surface area after the heat treatment.

Example 8 Heat treatment U prepared in Example 7
A5605 0.66 g, dimethyl carbonate (DMC)
2.0 g, DEC 2.0 g, EC 2.0 g, Hashimoto Chemicals LiP
0.60 g of F ₆ was mixed well at room temperature in an argon atmosphere to prepare an electrolytic solution. The water content (Karl Fischer method) of this electrolytic solution was 25 ppm. Free acid (HF conversion) is 2
It was 0 ppm or less (neutralization titration method). 25 of this electrolyte
The ionic conductivity at -10 ° C and -10 ° C was measured by the impedance method, and the values were 6.3 × 10 ^-3 and 1.5 × 10 ^-3 S /, respectively.
cm. Further, the viscosity measured with a rotational viscometer at room temperature (25
° C) was 30 cps (380 s ^-1 ).

Example 9 <Production of Lithium Cobaltate Cathode> 11 g of Li ₂ CO ₃
And 24 g of Co ₃ O ₄ are mixed well, and the mixture is
After heating at 0 ° C. for 24 hours, pulverization is performed to obtain LiCoO.
_Two powders were obtained. This LiCoO ₂ powder, acetylene black, and polyvinylidene fluoride were mixed at a weight ratio of 8: 1: 1, and an excess N-methylpyrrolidone solution was added to obtain a gel composition. The composition was applied on an aluminum foil of about 25 μm to a thickness of about 180 μm and molded. Furthermore, by heating and vacuum drying at about 100 ° C. for 24 hours, a lithium cobaltate positive electrode sheet was obtained. This sheet was punched into a 14 mmφ (115 mg) sheet with a punch to provide a positive electrode for a battery.

Example 10 <Production of Graphite Anode> MCMB graphite (manufactured by Osaka Gas), vapor-grown graphite fiber (manufactured by Showa Denko KK: average fiber diameter: 0.3 μm,
Excessive N-methylpyrrolidone solution was added to a mixture having an average fiber length of 2.0 μm and a heat treatment at 2700 ° C.) and a weight ratio of polyvinylidene fluoride of 8.6: 0.4: 1.0 to obtain a gel composition. This composition was coated on a copper foil of about 15 μm in a thickness of about 250 μm.
And molded to a thickness of Furthermore, the resultant was vacuum-dried at about 100 ° C. for 24 hours to obtain a graphite negative electrode sheet.
This sheet was punched into a 15 mmφ (62 mg) sheet with a punch to form a negative electrode for a battery.

Example 11 <Production of Li-ion secondary battery> The graphite negative electrode (15 mm) produced in Example 10 was placed in an argon atmosphere glove box.
φ) to the electrolyte solution prepared in Example 2 (UA5805 / Li)
PF ₆ / DEC + EC system). On the graphite negative electrode, a polyolefin microporous film manufactured by Asahi Kasei: a product obtained by impregnating the electrolyte prepared in Example 2 into a hypopore (porosity: about 65%, thickness: 25 μm) was attached.
Further, the lithium cobaltate positive electrode (1
4 mmφ), which was impregnated with the electrolytic solution prepared in Example 2, was attached, and a 2016 coin-shaped can (20 mm in diameter,
(Thickness: 1.6 mm) and sealed with graphite / cobalt oxide Li
An ion coin battery was obtained.

The battery was operated at an operating voltage of 2.75 to 4.1 V and a current of
When the charge and discharge were repeated at 0.77 mA, the maximum discharge capacity was 1
At 1.0 mAh, the cycle life before the capacity was reduced to 50% was 710 cycles. In addition, this battery
When charging and discharging were repeated at 2.5 to 4.2 V and current of 11 mA,
The maximum discharge capacity was 10.5 mAh, and the cycle life until the capacity was reduced to 50% was 630 times.

[Example 12] <Manufacture of Li-ion secondary battery> Instead of the electrolyte used in Example 11, the electrolyte prepared in Example 4 (aluminum oxide C / LiPF ₆ / DEC + EC system) was used. A 2016 type graphite / cobalt oxide-based Li-ion coin battery was obtained in the same manner as in Example 11 except for the difference. This battery
When charging and discharging were repeated at an operating voltage of 2.75 to 4.1 V and a current of 0.77 mA, the maximum discharge capacity was 11.3 mAh, and the cycle life until the capacity was reduced to 50% was 780 times. When the battery was repeatedly charged and discharged at an operating voltage of 2.5 to 4.2 V and a current of 11 mA, the maximum discharge capacity was 10.8 mAh.
And the cycle life until the capacity is reduced to 50% is 70
It was 0 times.

[0046]

The organic electrolyte solution of the present invention contains an electrolyte salt, an organic solvent, and alumina-based fine particles, has high ionic conductivity and good cation mobility, and improves current characteristics and energy density of a lithium ion battery. I was able to. The organic electrolyte solution of the present invention has a high surface activity at a low moisture content and is added with alumina-based fine particles having a high specific surface area, and has a small amount of impurities and a high ability to adsorb impurities of other materials. It was excellent, and the cycle life of the lithium ion battery could be improved.

Claims (11)

[Claims] 1. An organic electrolytic solution containing at least one kind of alumina-based fine particles, at least one kind of organic solvent, and at least one kind of electrolyte salt, wherein the alumina-based fine particles have a BET specific surface area of 10 m ² / g or more and a maximum diameter of 5 μm or less. An organic electrolyte having a water content (Karl Fischer titration value) of 3000 ppm or less and an addition amount of 0.05 to 30% by weight of the whole electrolyte. 2. The electrolyte has a viscosity of 2000 cps at room temperature.
2. The electrolyte solution according to claim ¹ , wherein the water content (Karl Fischer titration value) of the electrolyte is 200 ppm or less, and the free acid content (neutralization titration value) of the electrolyte is 100 ppm or less at a shear rate of 20 to 400 s ^-1 or less. Organic electrolyte. 3. An alumina-based fine particle having a temperature of 600 to 1200 ° C.
The organic electrolytic solution according to claim 1 or 2, wherein the organic electrolytic solution is γ-alumina heat-treated in (1). 4. An alumina-based fine particle having a temperature of 600 to 1200 ° C.
The organic electrolytic solution according to claim 1 or 2, wherein the organic electrolytic solution is an alkali metal / aluminum composite oxide that has been heat-treated in (1). 5. The method according to claim 1, wherein the alumina-based fine particles have a crystal particle diameter of 0.1 μm.
m, wherein the size of the primary particles is 0.01 to 5 μm.
5. The organic electrolytic solution according to any one of 4. 6. The organic electrolyte solution according to claim 1, wherein the electrolyte salt is at least one selected from an alkali metal salt, a quaternary ammonium salt, a quaternary phosphonium salt, and a transition metal salt. 7. The method according to claim 7, wherein the at least one electrolyte salt is LiPF.
₆ , LiBF ₄ and / or LiN (CF ₃ SO ₂ ) ₂
The organic electrolyte according to claim 6, wherein 8. The method according to claim 1, wherein the at least one organic solvent is cyclic and / or
The organic electrolytic solution according to any one of claims 1 to 7, wherein the organic electrolytic solution is a chain carbonate. 9. A battery using at least one organic electrolyte according to claim 1. 10. The lithium according to claim 9, wherein as the negative electrode active material, at least one material selected from the group consisting of lithium, lithium alloy, a carbon material capable of inserting and extracting lithium ions, an inorganic oxide and an inorganic chalcogenide is used. Secondary battery. 11. The lithium secondary battery according to claim 10, wherein a material comprising a conductive polymer, a metal oxide, a metal sulfide, and / or a carbon material is used as the positive electrode active material.