JP3095268B2 - Organic electrolyte and organic electrolyte battery using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic electrolyte and an organic electrolyte battery using the same.

[0002]

2. Description of the Related Art An organic electrolyte battery typified by a lithium-manganese dioxide battery using an anode made of lithium, a cathode made of a mixture containing manganese dioxide as a positive electrode active material, and an organic electrolyte is a high energy battery. Because of its high density, light weight, and long life, the demand tends to increase.

By the way, most of the organic electrolyte batteries use a mixture in which lithium is used for the negative electrode and manganese dioxide is used as the positive electrode active material for the positive electrode, as described above. The improvement mainly depends on how to improve the performance of the organic electrolyte.

In order to improve the output characteristics of a battery using this organic electrolyte, it is necessary to increase the conductivity of the organic electrolyte and reduce the impedance (resistance) of the battery. Also, in this organic electrolyte battery, a highly reactive alkali metal is used for the negative electrode, and a flammable organic solvent is used for the solvent of the electrolyte, so that the organic electrolyte has a conductivity as described above. It is necessary to have not only improvement but also safety.

[0005] However, there has been a problem that the organic electrolytes which have been used so far lack the safety if they are intended to improve the conductivity, and have insufficient conductivity if the safety is considered.

For example, as described in JP-A-59-214163, L which has been generally used so far
iClO ₄ / PC: DME-based organic electrolyte [propylene carbonate (PC) and 1,2-dimethoxyethane (D
Dissolved LiClO _{4 in} a mixed solvent with ME)
Although there is a high conductivity, there is a problem that LiClO _{4 as} an electrolyte has a high risk and lacks safety.

Also, LiCF ₃ SO ₃ / PC: DME based organic electrolyte [propylene carbonate (PC) and 1,2-
LiCF _{3 in} a mixed solvent with dimethoxyethane (DME)
Which was dissolved SO _3] is always safety not be said as sufficient, LiCF ₃ highly further secure than SO ₃ Li
The conductivity of the C ₄ F ₉ SO ₃ -based organic electrolyte was not sufficient.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the conventional organic electrolyte and develops an organic electrolyte having high conductivity while ensuring the safety of the organic electrolyte. It is another object of the present invention to provide an organic electrolyte battery having low impedance by using the organic electrolyte.

[0009]

SUMMARY OF THE INVENTION The present invention uses vinylene carbonate as a solvent for the organic electrolyte, and the electrolyte
By using LiC _n F _{2n + 1} SO ₃ (n ≧ 4), the conductivity of the organic electrolyte is improved while ensuring safety, and the impedance of the battery is reduced by using this organic electrolyte. It has been lowered.

The progress of completing the present invention will be described in detail as follows.

[0011] The present inventors firstly used LiC as an electrolyte.
The conductivity of organic electrolytes of various solvent systems using ₄ F ₉ SO ₃ was examined, and LiC ₄ F ₉ SO ₃ / EC: DME (1:
2) system organic electrolyte [volume ratio of ethylene carbonate (EC) and 1,2-dimethoxyethane (DME) 1: 2
Dissolving LiC ₄ F ₉ SO ₃ in a mixed solvent of the above) has high conductivity.

However, the above-mentioned organic electrolyte is -10 ° C.
In the vicinity, there is a problem that the material starts to be solid and the conductivity is abnormally reduced.

Therefore, in order to lower the freezing point of the organic electrolytic solution, an unsaturated bond is introduced into a part of the skeleton structure of ethylene carbonate, and the resulting vinylene carbonate is used in place of ethylene carbonate.
An organic electrolyte solution of iC ₄ F ₉ SO ₃ / VC: DME (1: 2) [Li in a mixed solvent of vinylene carbonate (VC) and 1,2-dimethoxyethane (DME) in a volume ratio of 1: 2.
C ₄ F ₉ SO ₃ dissolved in 0.3 mol / l] was prepared, and its conductivity was examined.

As a result, the conductivity of the above-mentioned organic electrolyte can be measured even at −20 ° C., and the conductivity at a low temperature (−20 ° C.) is much lower than that of the ethylene carbonate-based organic electrolyte. The inventors have found that the present invention is improved, and completed the present invention.

In the present invention, in preparing the organic electrolyte, the above vinylene carbonate can be used in combination with another organic solvent. Examples of such an organic solvent which can be used in combination include 1,2-dimethoxyethane, dimethoxymethane, dimethoxypropane, 1,3-dioxolan, tetrahydrofuran, 2-methyltetrahydrofuran,
Ethers such as -methyl-1,3-dioxolane; esters such as propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone; and sulfolane.

In particular, in order to obtain a battery having excellent discharge characteristics at low temperatures, it is preferable to use 1,2-dimethoxyethane, which has a low freezing point and a large effect of improving conductivity, among the above-mentioned organic solvents.

In preparing the organic electrolyte, the amount of vinylene carbonate used is preferably at least 10% by volume, particularly preferably at least 20% by volume in the total solvent. This means that if vinylene carbonate is less than 10% by volume in the total solvent,
This is because the effect of increasing the conductivity of the organic electrolyte and lowering the impedance of the battery is not sufficiently exhibited.

Although the above-mentioned vinylene carbonate alone can constitute the entire solvent of the organic electrolyte, considering the conductivity at low temperatures, the amount of vinylene carbonate used is 50% by volume or less, preferably 40% by volume, of the total solvent. It is preferred to keep the volume% or less.

Further, in preparing the organic electrolyte,
When an ether such as 2-dimethoxyethane is used in combination,
Their ethers are 50-90% by volume, in particular 60-80%
It is preferred to be volume%. In other words, if too much ether is added, solidification at low temperatures is unlikely to occur, but the conductivity is reduced.If too little ether is used, the conductivity at low temperatures is reduced, and when used in batteries. The impedance increases.

When an ester such as propylene carbonate is used in combination with vinylene carbonate, it is preferable to keep the total amount of those esters at 50% by volume or less, particularly 40% by volume or less in the total solvent.

In preparing the organic electrolytic solution of the present invention, LiC _n F _{2 n + 1} SO ₃ (n ≧ 4 ) is used as the electrolyte. The LiC _n F _{2n + 1} SO ₃ has Li ₂ (C _m
F _2m ) (SO ₃ ) ₂ , LiN (C _m F _{2m + 1} SO ₂ ) ₂ ,
LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ CO) ₂ ,
LiC (CF ₃ CO) ₃ , LiC _m F _{2m + 1} CO ₂ , Li
_{B (C 6 H 5) 4} , LiPF 6, LiA S F 6, LiS
It is also possible to use a mixture of bF ₆ and LiBF ₄ . In the above chemical formula, n and m are integers.

In the present invention, LiC _n F _{2n + 1} SO
₃ (n ≧ 4 ) is used as an essential electrolyte because LiC
_{This is because n} F _{2n + 1} SO ₃ (n ≧ 4 ) is excellent in safety.

In the present invention, Li is used as an essential electrolyte.
The use of C _n F _{2n + 1} SO ₃ (n ≧ 4 ) is as described above.
The reason is that LiC _n F _{2n + 1} SO ₃ (n ≧ 4) is particularly high in safety. However, when n is 4 or more, the conductivity is low in a normal solvent system and the conductivity is high. Organic electrolyte cannot be obtained. However, in the solvent system of the present invention using vinylene carbonate, the conductivity can be increased. Therefore, even when n is 4 or more, an organic electrolyte having high conductivity is obtained, and n is 4 or more. Can make better use of the high security of

Then, LiC _n F _{2n + 1} SO ₃ (n ≧ 4 )
Is 0.1 to 2.5 mol in preparing the organic electrolyte solution.
/ L, particularly preferably 0.2 to 0.7 mol / l. When other electrolytes are used together, they are 1 m
It is preferably used in a range of at most ol / l, particularly at most 0.7 mol / l.

Next, main components of the battery will be described.

In the present invention, the negative electrode comprises an alkali metal or a compound containing an alkali metal integrated with a current collecting material such as a stainless steel net. Examples of the alkali metal include lithium, sodium and potassium. Examples of the compound containing an alkali metal include an alloy of an alkali metal and aluminum, lead, indium, potassium, cadmium, tin, magnesium, or the like, a compound of an alkali metal and a carbon material, and a low-potential alkali metal and a metal. Compounds with oxides and sulfides are exemplified.

For the positive electrode, for example, a positive electrode active material such as manganese dioxide, vanadium pentoxide, chromium oxide, lithium cobalt oxide and lithium nickel oxide, or a conductive auxiliary or polytetrafluoroethylene such as Of a mixture obtained by appropriately adding a binder or the like to a molded body using a current collecting material such as a stainless steel net as a core material is used.

[0028]

Next, the present invention will be described more specifically with reference to examples.

EXAMPLE 1 A mixed solvent of VC: DME having a volume ratio of 1: 2 [vinylene carbonate (VC) and 1,2-dimethoxyethane (DM)
E: mixed solvent with a volume ratio of 1: 2) to LiC ₄ F ₉ SO
₃ was dissolved in 0.3 mol / l to prepare an organic electrolyte solution.

Further, a heat-treated manganese dioxide mixture comprising a mixture of manganese dioxide, carbon black and polytetrafluoroethylene is formed into a sheet having a thickness of 0.4 mm and a width of 30 mm using a stainless steel net as a core material,
A 250-inch strip cathode with a stainless steel current collector attached
C., dried, and then cooled to room temperature in a dry atmosphere.

Next, the above-mentioned band-shaped positive electrode was wrapped with a separator made of a microporous polypropylene film having a thickness of 25 μm, and a sheet-shaped lithium having a thickness of 0.18 mm and a width of 30 mm was pressure-bonded to a stainless steel net. Stack,
After spirally winding into a spiral electrode body, the outer diameter is 15 mm
Was filled in the bottomed cylindrical battery case, and the positive electrode lead body and the negative electrode lead body were spot-welded, and then the above-mentioned organic electrolyte was injected into the battery case.

Next, the opening of the battery case was sealed in a conventional manner to produce a cylindrical organic electrolyte battery having the structure shown in FIG.

Referring to the battery shown in FIG. 1, reference numeral 1 denotes the positive electrode and 2 denotes the negative electrode. However, in FIG. 1, in order to avoid complication, stainless steel nets, current collectors, and the like used in manufacturing the positive electrode 1 and the negative electrode 2 are not shown. Reference numeral 3 denotes a separator, and reference numeral 4 denotes the above electrolyte.

5 is a stainless steel battery case,
This battery case 5 also serves as a negative electrode terminal. An insulator 6 made of a polytetrafluoroethylene sheet is provided at the bottom of the battery case 5, and an insulator 7 made of a polytetrafluoroethylene sheet is also provided at the inner periphery of the battery case 5. The spiral electrode body including the negative electrode 2 and the separator 3, the electrolyte 4, and the like are accommodated in the battery case 5.

Reference numeral 8 denotes a sealing plate made of stainless steel, and a gas ventilation hole 8a is provided in the center of the sealing plate 8. 9 is an annular packing made of polypropylene, 10 is a flexible thin plate made of titanium, and 11 is a thermally deformable member made of an annular polypropylene.

The above-mentioned heat deformable member 11 has an effect of changing the breaking pressure of the flexible thin plate 10 by being deformed by the temperature.

Reference numeral 12 denotes a nickel-plated rolled steel terminal plate. The terminal plate 12 is provided with a cutting edge 12a and a gas discharge hole 12b. When the internal pressure rises and the flexible thin plate 10 is deformed by the increase of the internal pressure, the flexible thin plate 10 is broken by the cutting blade 12a, and gas inside the battery is discharged from the gas discharge hole 12b to the outside of the battery. It is designed to discharge and prevent battery rupture.

Reference numeral 13 denotes an insulating packing, and 14 denotes a lead body. The lead body 14 electrically connects the positive electrode 1 and the sealing plate 8, and the terminal plate 12 is connected to the positive electrode terminal by contact with the sealing plate 8. Act as Reference numeral 15 denotes a lead body for electrically connecting the negative electrode 2 and the battery case 5.

Comparative Example 1 A mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DM) having a volume ratio of PC: DME of 1: 2
E: mixed solvent with a volume ratio of 1: 2) to LiC ₄ F ₉ SO
₃ was dissolved in 0.3 mol / l to prepare an organic electrolyte solution.

Example 1 was repeated except that this organic electrolyte was used.
In the same manner as in the above, a cylindrical organic electrolyte battery was produced.

Comparative Example 2 A mixed solvent of EC: DME having a volume ratio of 1: 2 [ethylene carbonate (EC) and 1,2-dimethoxyethane (DM)
E: mixed solvent with a volume ratio of 1: 2) to LiC ₄ F ₉ SO
₃ was dissolved in 0.3 mol / l to prepare an organic electrolyte solution.

Example 1 was repeated except that this organic electrolyte was used.
In the same manner as in the above, a cylindrical organic electrolyte battery was produced.

The characteristics of the batteries of Example 1 and Comparative Examples 1-2 prepared as described above and the organic electrolyte used for the batteries were evaluated.

First, the organic electrolyte solution used in the battery of Example 1 and the organic electrolyte solution used in the batteries of Comparative Examples 1-2 were compared.
The ionic conductivity at 20 ° C., 0 ° C. and 20 ° C. was measured. Table 1 shows the results.

[0045]

[Table 1]

The organic electrolyte of Comparative Example 1 is the most common solvent-based organic electrolyte that has been conventionally used. As shown in Table 1, the organic electrolyte of Example 1 was At all temperatures, the ionic conductivity was higher than that of the organic electrolyte of Example 1.

The organic electrolyte of Comparative Example 2 used ethylene carbonate as a solvent.
Although the ionic conductivity was higher than the organic electrolyte solution of Comparative Example 1 at -20 ° C, the ionic conductivity was not measured at -20 ° C, and the ionic conductivity could not be measured.

Next, the impedance of the battery of Example 1 and the battery of Comparative Example 1 at 1 kHz was measured. Table 2 shows the results.

[0049]

[Table 2]

As shown in Table 2, the battery of Example 1 had lower impedance than the battery of Comparative Example 1 using the conventional solvent system.

Next, in order to confirm the safety of the battery of Example 1, as Comparative Example 3, batteries using LiClO ₄ as an electrolyte were manufactured, and a test for confirming the safety of these batteries was performed. . The test method and test results for producing the battery of Comparative Example 3 and confirming the safety are shown below.

Comparative Example 3 A mixed solvent of PC: DME having a volume ratio of 1: 2 [propylene carbonate (PC) and 1,2-dimethoxyethane (DM)
0.3 mol / l of LiClO ₄ was dissolved in a mixed solvent having a volume ratio of 1: 2 with E) to prepare an organic electrolyte solution.

The method using this organic electrolyte was described in Example 1.
In the same manner as in the above, a cylindrical organic electrolyte battery was produced.

The battery of Example 1, the battery of Comparative Example 1, and the battery of Comparative Example 3 were each overdischarged at 100 A to -3 V at 10 A, and after reaching -3 V, a constant voltage discharge of -3 V was performed. Then, the occurrence rate at which the battery surface temperature generates heat of 150 ° C. or more (abnormal heat generation) or breakage was examined. Table 3 shows the results.

[0055]

[Table 3]

As is clear from the results shown in Table 3, the battery of Example 1 was superior in safety to the battery of Comparative Example 3.

[0057]

As described above, in the present invention, vinylene carbonate is used as the solvent, and Li is used as the electrolyte.
By using C _n F _{2n + 1} SO ₃ (n ≧ 4 ), the conductivity is higher than that of an organic electrolyte using a conventional solvent system in a temperature range of −20 ° C. to 20 ° C. while ensuring safety. An organic electrolyte was obtained.

Further, by using the above-mentioned organic electrolyte, an organic electrolyte battery having high safety and small impedance could be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of an organic electrolyte battery according to the present invention.

[Explanation of symbols]

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

Continued on the front page (72) Inventor Katsuaki Hasegawa 1 Tohocho, Yokkaichi City, Mie Prefecture Mitsubishi Yuka Co., Ltd. Inside Yokkaichi Research Institute (72) Inventor Makio Kimura 1 Tohocho, Yokkaichi City, Mie Prefecture Mitsubishi Yuka Co., Ltd. (56) References JP-A-2-244565 (JP, A) JP-A-2-215059 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 6/16 H01M 10/40

Claims (4)

(57) [Claims] 1. An organic electrolytic solution comprising vinylene carbonate as a solvent and LiC _n F _{2n + 1} SO ₃ (n ≧ 4 ) as an electrolyte. 2. The organic electrolyte according to claim 1, wherein the solvent contains 1,2-dimethoxyethane. 3. An organic electrolyte battery comprising: a negative electrode comprising an alkali metal or a compound containing an alkali metal; a positive electrode; and the organic electrolyte according to claim 1. 4. The organic electrolyte battery according to claim 3, wherein 1,2-dimethoxyethane is contained as a solvent in the organic electrolyte.