JPH05283086A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To improve the low temperature chracteristic of the organic electrolyte battery having a negative electrode made of alkali metal, alkaline earth metal or the compound containing them. CONSTITUTION:As electrolyte of the organic electrolytic solution, metallic salt having two or more of RfSO2 group (Rf=F or fluoroalkyl group) such as (CF3SO2)2NLi is used, and as solvent, annular ether such as 3-dioxiolan and ethylene carbonate are used, and as positive electrode active material, metal oxide having a large surface area at 15m<2>/g or more of BET specific surface area (for example, manganese dioxide) is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electrolyte battery, and more particularly to improvement of the organic electrolyte solution (hereinafter, simply referred to as "electrolyte solution" except for expressing the name of the battery).

[0002]

2. Description of the Related Art Organic electrolyte batteries represented by manganese dioxide-lithium batteries have a high voltage, a long life, and a high energy density, and therefore their markets are expanding year by year. In order to improve the safety, LiC _n F _{2n + 1} SO ₃ -based organic lithium salt represented by LiCF ₃ SO ₃ is widely used instead of perchloric acid-based LiClO ₄ as an electrolyte. It's coming. However, the conductivity of LiCF ₃ SO _{3 and the} like is lower than that of LiClO ₄ used conventionally, and the battery characteristics generally tend to deteriorate.

Therefore, recently, (CF ₃ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) has been used in place of LiCF ₃ SO _3, etc.
It has been proposed to use ₃ CLi or the like as an electrolyte [L. A. Dominey, Fifth Inter
national Seminar on Lithi
um Battery Technology and
Applications, March 4-6, 1
(1991)].

These new lithium salts are LiCF ₃
The conductivity is far superior to that of SO _3, etc.
It has a conductivity about twice as _{high as} that of CF ₃ SO ₃ . Usually, if the conductivity is high, it is expected that the low temperature characteristics of the battery will be improved, but the inventors of the present invention have studied that LiCF ₃ SO ₃ / PC: DME electrolytic solution [propylene carbonate (PC) and instead of LiCF ₃ SO ₃ of 1,2-dimethoxyethane (DME) and an electrolyte solution obtained by dissolving LiCF ₃ SO ₃ in a mixed solvent of], (CF ₃ SO
₂ ) The use of ₂ NLi did not improve the low temperature characteristics of the battery.

[0005]

As described above, the present invention provides a RfSO ₂ group such as (CF ₃ SO ₂ ) ₂ NLi [R
f is an organic electrolyte battery using a metal salt having two or more F (fluorine) or fluoroalkyl groups] solved the problem that the low temperature characteristics could not be improved despite having high conductivity, It is an object to provide an organic electrolyte battery having excellent low temperature characteristics.

[0006]

The present invention improves the low temperature characteristics of a battery by using a metal salt having two or more RfSO ₂ groups as an electrolyte of an organic electrolyte battery and using a cyclic ether as a solvent. However, the above-mentioned object is achieved.

The process of completing the present invention will be described in detail below.

The present inventors first investigated the solvent composition in order to improve the conductivity of the LiCF ₃ SO ₃ system electrolyte. As a result, it was found that the PC: DME system had excellent conductivity and also had the best low-temperature characteristics. The use of 1,3-dioxolane or the like was also examined, but the conductivity decreased rather. Also, ethylene carbonate was added.
In this case, the conductivity is improved, but if too much ethylene carbonate is added, the electrolytic solution will start to solidify at low temperature, rather lowering the low temperature characteristic, and if it is reduced, the conductivity will be slightly higher but the low temperature characteristic will not be improved. It was

Therefore, in order to further improve the low-temperature characteristics, it is considered to study an electrolytic solution having _two CF ₃ SO ₂ groups and having a large conductivity improving effect (CF ₃ SO ₂ ) ₂ NLi. It was

The reason why the conductivity is improved by using this (CF ₃ SO ₂ ) ₂ NLi as an electrolyte is that LiCF ₃ SO ₃ used conventionally is CF ₃ SO ₂ (O) L of the following formula.
Like i, only one CF ₃ SO ₂ group is attached to the O atom (oxygen atom) adjacent to Li (lithium), so that the electron density on this O atom is increased and Li ⁺ is released. And becomes difficult to ionize, while (CF ₃ SO ₂ ) ₂
NLi has CF on the N atom (nitrogen atom) adjacent to Li.
_It is considered that since two ₃ SO ₂ groups are attached and electrons are attracted, the electron density on the N atom becomes lower, resulting in easier ionization and improved conductivity. Therefore, it is expected that by adding more electron-withdrawing groups such as CF ₃ SO ₂ groups to the atoms adjacent to Li, ionization of the electrolyte is promoted and higher conductivity can be obtained.

This high conductivity can be expected (CF ₃ SO
₂ ) ₂ NLi and LiCF ₃ SO ₃ used conventionally were compared in conductivity with PC: DME system, which has the best low-temperature characteristics of LiCF ₃ SO ₃ , and found 0.6 MLiCF.
₃ SO ₃ / PC: DME (1: 2) [propylene carbonate (PC) and 1,2-dimethoxyethane (DME)
LiCF ₃ SO ₃ was added to a mixed solvent having a volume ratio of 1: 2 with LiCl ₃ SO ₃ .
6 mol / l (M) dissolved] has a conductivity of −20.
It is 3.3 mS / cm at 30 ° C. and 6.1 mS / cm at 30 ° C., while it is 0.6 M (CF ₃ SO ₂ ) ₂ NLi / P.
C: DME (1: 2) [Propylene carbonate and 1,
In a mixed solvent with 2-dimethoxyethane in a volume ratio of 1: 2, (CF ₃ SO ₂ ) ₂ NLi was dissolved at 0.6 mol / l], 5.6 mS / cm at -20 ° C and 1 at 30 ° C.
It was 3.8 mS / cm, and the conductivity was about twice as high.

Therefore, a cylindrical lithium battery as shown in FIG. 1 was produced using this (CF ₃ SO ₂ ) ₂ NLi-based electrolytic solution, and the pulse discharge characteristics at low temperature were actually investigated.
Unexpectedly, the low-temperature characteristics were not improved, and a so-called delay phenomenon, in which the discharge voltage of the battery dropped at the beginning of discharge, appeared. Therefore, when the effect of the combination of solvents and the composition ratio was further investigated, it was surprisingly found that cyclic ethers such as 1,3-dioxolane, which was not effective in improving the conductivity and the low temperature characteristics in LiCF ₃ SO ₃ , were found to be surprising. It was found that the low temperature characteristic was further improved by adding the ethylene carbonate, and the present invention was completed.

In the present invention, RfSO is used as the electrolyte.
₂ group using a metal salt having two or more, but this Rf is F
Alternatively, as a metal contained in the metal salt, which is a fluoroalkyl group, for example, Li, Na, Cs, Ca,
Examples include Mg, Al, B, P, Ga, Si, As, Sb and the like. However, when lithium or a lithium compound is used for the negative electrode, Li (lithium) is most suitable as the metal in the metal salt.

A typical example of the metal salt having two or more RfSO ₂ groups is (CF ₃ SO ₂ ) ₂ NL.
i, (CF ₃ SO ₂ ) ₃ CLi and the like. In these metal salts, it is very important for the atom adjacent to the metal such as Li to bond with two or more substituents having a large electron-withdrawing property having an RfSO ₂ group for improving the conductivity of the electrolytic solution. is there.

When the metal salt having two or more RfSO ₂ groups is used as an electrolyte, the concentration is usually 1 M (m
ol / l) maximizes the conductivity, but if importance is attached to the characteristics at low temperatures, 0.2 to 0.8 M, especially 0.4 to
0.6M is preferred. When the concentration is 0.4 M or more, the low-temperature characteristics are improved even when the conventional solvent composition, for example, PC: DME system is used, but when the concentration is increased, the delay at low temperature becomes large, and the voltage at the initial stage of discharge is the device using the battery. The operating voltage may drop below the operating voltage of, and the operation of the device using the battery may be delayed.

In the present invention, it is an essential condition to use a cyclic ether as a solvent for the electrolytic solution. Examples of the cyclic ether include 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, 1,3,5. -Trioxane, their derivatives, etc. are mentioned, Among them, 1,3-dioxolane is preferable. The amount of the cyclic ether used is preferably half or more in all the solvents, more preferably 60 to 90% by volume, further preferably 65 to 80% by volume. That is, this cyclic ether contributes to the improvement of low-temperature characteristics, but if it is too much, the storage property may be deteriorated. Therefore, it is preferable to use the cyclic ether while considering the upper limit of the amount used.

When ethylene carbonate is added, the low temperature characteristics are further improved. However, the ratio of ethylene carbonate is preferably half or less, more preferably 10 to 40% by volume, further preferably 20 to 3%.
It is 5% by volume. That is, although this ethylene carbonate contributes to the improvement of low temperature characteristics when used within a specific range,
If the amount is too large, the electrolytic solution will start to solidify at a low temperature and will rather deteriorate the low temperature characteristics. Therefore, it is preferable to use the electrolytic solution in consideration of the upper limit of the addition amount thereof.

In addition to the above cyclic ethers and ethylene carbonates, carbonates such as propylene carbonate, butylene carbonate, diethylene carbonate, dimethyl carbonate and vinylene carbonate, esters such as γ-butyrolactone, 1, 2
-Chain ethers such as dimethoxyethane and diglyme, as well as sulfolane, dichloromethane, trimethyl phosphate, nitriles, and amides can be appropriately used. However, when these carbonates or esters are used, it is preferable that the combined amount of them and ethylene carbonate be used within the range of the amount described for the ethylene carbonate, and chain ethers are used. In such a case, it is preferable that the combined amount of the cyclic ether and the cyclic ether is within the range of the amount described for the cyclic ether.

In the present invention, as the positive electrode, for example, a positive electrode active material such as manganese dioxide, manganese pentoxide, chromium oxide, lithium cobalt oxide, lithium nickel oxide or the like, or carbon black or graphite may be used as the positive electrode active material. A positive electrode mixture to which a conductive auxiliary agent or a binder such as polytetrafluoroethylene is appropriately added is molded together with a current collecting material such as stainless steel or aluminum to form a molded body.

If importance is attached to low-temperature characteristics, it is preferable to use a positive electrode active material having a large surface area. For example, taking manganese dioxide as an example, the surface area before heat treatment is about 40 m ² / g (the BET specific surface area after heat treatment is 1
0 m ² / g) and BET specific surface area of 15 m ² / g compared to manganese dioxide that has been generally used for lithium batteries.
As described above, by using manganese dioxide having a BET specific surface area of 20 m ² / g or more, and further preferably having a BET specific surface area of 30 m ² / g or more, a battery having better low-temperature characteristics can be obtained. In addition, manganese dioxide B
All ET specific surface areas are for manganese dioxide after heat treatment.

However, conventional electrolytes such as PC:
BET specific surface area 1 even when using DME electrolyte
The use of manganese dioxide of 5 m ² / g or more improves the low temperature characteristics, but on the other hand, the voltage drop at the initial stage of discharge,
The so-called delay phenomenon becomes large. But,
In the electrolytic solution system of the present invention, even if such a positive electrode active material having a large surface area is used, the delay phenomenon does not increase, and the excellent positive electrode active material ability can be more effectively exhibited.

For the negative electrode, an alkali metal such as lithium, sodium or potassium, an alkaline earth metal such as calcium, or a compound containing these metals is used. Of these, lithium or a compound containing lithium is most suitable.

[0023]

[Embodiment 1] Next, the present invention will be described more specifically with reference to embodiments. However, the present invention is not limited to these examples.

Example 1 A positive electrode mixture comprising 90 parts by weight of manganese dioxide having a BET specific surface area of 30 m ² / g, 5 parts by weight of carbon black having a particle size of 150 μm or more, and 5 parts by weight of polytetrafluoroethylene having an average particle size of 0.3 μm. After the agent was made into a paste with water and alcohol, a sheet-like positive electrode formed into a sheet with a thickness of 0.4 mm, a width of 30 mm and a length of 200 mm was prepared, dried at 250 ° C. for 9 hours, and then dried in a dry atmosphere. Cooled to room temperature.

Next, this sheet-like positive electrode is formed to a thickness of 25 μm.
Wrapped in a separator made of microporous polypropylene film of 0.18 mm, width 30 mm, length 19
Sheet-shaped negative electrodes made of 0 mm of lithium were stacked and spirally wound to form a spiral electrode body, which was then loaded into a cylindrical battery case having a bottom and spot welding of a lead body was performed.

Then, in the battery case, 0.6M
(CF ₃ SO ₂ ) ₂ NLi / EC: Diox (1: 2)
[In a mixed solvent of ethylene carbonate (EC) and 1,3-dioxolane (Diox) at a volume ratio of 1: 2 (CF ₃
SO ₂ ) ₂ NLi dissolved in 0.6 mol / l] as an electrolytic solution was injected in an amount of 2 cc, the opening of the battery case was sealed, and stabilization treatment was performed to form a cylindrical organic electrolytic solution having the structure shown in FIG. A battery was produced.

Explaining the battery shown in FIG. 1, reference numeral 1 is a positive electrode formed by molding the positive electrode mixture containing manganese dioxide as a positive electrode active material, and a stainless steel net also serves as a current collecting core during the molding. It is used as a material,
In FIG. 1, a stainless steel net is not shown in order to avoid complication. Reference numeral 2 denotes a negative electrode made of lithium, and a stainless steel net is also used as a support also having a current collecting function in the production of the negative electrode 2. However, in FIG. Is not shown. 3 is a separator made of a microporous polypropylene film, and 4 is the above-mentioned electrolytic solution.

Reference numeral 5 denotes a stainless steel battery case,
The battery case 5 also serves as a negative electrode terminal. An insulator 6 made of a polytetrafluoroethylene sheet is installed on the bottom of the battery case 5, and an insulator 7 made of a polytetrafluoroethylene sheet is also installed on the inner peripheral part of the battery case 5. The spiral electrode body including the negative electrode 2 and the separator 3, the electrolytic solution 4, and the like are housed in the battery case 5.

Reference numeral 8 is a stainless steel sealing plate, and a gas vent hole 8a is provided in the central portion of the sealing plate 8. Reference numeral 9 is a polypropylene annular packing, 10 is a titanium flexible thin plate, and 11 is an annular polypropylene thermal deformation member.

The thermal deformation member 11 acts to change the breaking pressure of the flexible thin plate 10 by being deformed by the temperature.

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

Reference numeral 13 is an insulating packing, and 14 is a lead body. This lead body 14 electrically connects the positive electrode 1 and the sealing plate 8, and the terminal plate 12 comes into contact with the sealing plate 8 to make a positive electrode terminal. Acts as. Reference numeral 15 is a lead body that electrically connects the negative electrode 2 and the battery case 5.

Example 2 A tubular organic electrolyte battery was produced in the same manner as in Example 1 except that manganese dioxide having a small BET specific surface area of 10 m ² / g and a small specific surface area was used as the positive electrode active material.

Example 3 0.3 M (CF ₃ SO ₂ ) ₂ NLi / E as an electrolytic solution
A tubular organic electrolyte battery was produced in the same manner as in Example 1 except that C: Diox (1: 2) was used.

Comparative Example 1 0.6 M (CF ₃ SO ₂ ) ₂ NLi / P as an electrolytic solution
A tubular organic electrolyte battery was produced in the same manner as in Example 1 except that C: DME (1: 2) was used.

Comparative Example 2 A tubular organic electrolyte battery was prepared in the same manner as in Comparative Example 1 except that manganese dioxide having a BET specific surface area of 10 m ² / g was used as the positive electrode active material.

Comparative Example 3 0.3 M (CF ₃ SO ₂ ) ₂ NLi / P as an electrolytic solution
A tubular organic electrolyte battery was produced in the same manner as in Comparative Example 2 except that C: DME (1: 2) was used.

Comparative Example 4 0.6 M LiCF ₃ SO ₃ / PC: DME as an electrolytic solution
A tubular organic electrolyte battery was produced in the same manner as in Comparative Example 2 except that (1: 2) was used.

The batteries of Examples 1 to 3 and Comparative Examples 1 to 4 produced as described above were stored at −20 ° C. and 1.2 A × 3 s.
The minimum voltage in each pulse when pulse-discharged under the condition of on + 7s off was measured. Fig. 2 shows the relationship between the number of pulse discharges of each battery and the minimum voltage at each pulse.
~ Shown in FIG. However, in FIGS. 2 to 8, the lowest voltage in each pulse is simply shown as a voltage on the vertical axis.

FIG. 2 shows the relationship between the number of pulse discharges of the battery of Example 1 and the minimum voltage in each pulse.
As shown in FIG. 2, in the battery of Example 1, no delay (voltage drop) in the initial stage of discharge was observed, and 1.3 V (this 1.3 V is the minimum operating voltage of the equipment using this type of battery). ) The number of pulse discharges that can be kept above is 711 times, and these show excellent low-temperature characteristics as will be apparent from the comparison with the characteristics of the battery of the comparative example described below, particularly the characteristics of the battery of the comparative example 4. Is.

Therefore, first, the low temperature characteristics of the battery of Comparative Example 4 corresponding to the conventional battery will be described with reference to FIG.

The battery of Comparative Example 4 contained BE as the positive electrode active material.
Manganese dioxide having a T specific surface area of 10 m ² / g was used, and 0.6 M LiCF ₃ SO ₃ / PC: DME was used as an electrolytic solution.
Although the battery of the conventional configuration using (1: 2), the battery of Comparative Example 4 has a pulse discharge frequency of 248 times that can maintain 1.3 V or more, as shown in FIG.

Then, in the battery of Comparative Example 2 in which the electrolyte LiCF ₃ SO ₃ in the battery of Comparative Example 4 was changed to (CF ₃ SO ₂ ) ₂ NLi, as shown in FIG.
The number of pulse discharges that can maintain the above is reduced to 236, and a delay phenomenon is recognized at the initial stage of discharge.

Further, in the battery of Comparative Example 3 in which the concentration of (CF ₃ SO ₂ ) ₂ NLi was lowered to 0.3 M, as shown in FIG.
The number of pulse discharges that can maintain the above condition was further reduced to 172.

On the other hand, in the battery of Example 2, as the electrolytic solution, 0.6M (CF ₃ SO ₂ ) ₂ NLi / EC: Diox was used.
Although (1: 2) is used, as shown in FIG.
1.3V without delay phenomenon at the beginning of discharge
The number of pulse discharges that can maintain the above is 351 and Comparative Example 2
It was confirmed that the low temperature characteristics were improved more than 100 times more than the batteries No. 4 to No. 4.

In the battery of Comparative Example 1, BE was used as the positive electrode active material.
Since manganese dioxide having a T specific surface area of 30 m ² / g is used, as shown in FIG. 5, the number of pulse discharges that can maintain 1.3 V or more increases to 580, but a large delay phenomenon occurs at the initial stage of discharge. Occurs and lacks practicality.

As described above, the battery of Example 1 had no delay phenomenon at the initial stage of discharge as shown in FIG.
The number of pulse discharges that can maintain 3 V or more is 711 times, and the low-temperature characteristics are remarkably improved not only in the battery of Comparative Example 4 corresponding to the conventional battery but also in the batteries of other Comparative Examples. .. In addition, the battery of Example 1 has far more pulse discharge times capable of maintaining 1.3 V or more than the battery of Example 2 in which manganese dioxide having a BET specific surface area of 10 m ² / g was used as the positive electrode active material. Specific surface area 30m ²
The characteristic of using manganese dioxide having a large surface area of / g as a positive electrode active material is remarkably exhibited.

Further, as shown in FIG. 4, the battery of Example 3 has an excellent low temperature characteristic that there is no delay phenomenon at the initial stage of discharge and the number of pulse discharges that can maintain 1.3 V or more is as many as 614. Was there.

[0049]

As described above, in the present invention, a metal salt having two or more RfSO ₂ groups is used as an electrolyte,
And by using a cyclic ether as a solvent,
An organic electrolyte battery having excellent low temperature characteristics can be provided. Further, by using a positive electrode active material having a large surface area, it has become possible to provide an organic electrolyte battery with further improved low temperature characteristics.

[Brief description of drawings]

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

FIG. 2 is a graph showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Example 1.

FIG. 3 is a diagram showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Example 2.

FIG. 4 is a diagram showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Example 3.

FIG. 5 is a diagram showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Comparative Example 1.

FIG. 6 is a diagram showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Comparative Example 2.

FIG. 7 is a diagram showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Comparative Example 3.

FIG. 8 is a diagram showing the relationship between the number of pulse discharges and the minimum voltage in each pulse during low temperature heavy load pulse discharge of the battery of Comparative Example 4.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode 3 Separator 4 Electrolyte

Claims (4)

[Claims] 1. An organic electrolyte battery having a negative electrode made of an alkali metal, an alkaline earth metal or a compound containing these, a positive electrode, and an organic electrolyte, wherein an RfSO ₂ group (Rf = F) is used as an electrolyte of the organic electrolyte. Alternatively, an organic electrolyte battery comprising a metal salt having two or more fluoroalkyl groups and containing a cyclic ether as a solvent. 2. The organic electrolyte battery according to claim 1, wherein the metal salt having two or more RfSO ₂ groups is (CF ₃ SO ₂ ) ₂ NLi. 3. The organic electrolyte battery according to claim 1, which contains ethylene carbonate as a solvent. 4. The organic electrolyte battery according to claim 1, wherein a metal oxide having a BET specific surface area of 15 m ² / g or more is used as a positive electrode active material.