JPS6215771A - Organic electrolyte cell - Google Patents

Abstract

PURPOSE:To improve not only discharging voltage for a primary cell, but also efficiency of charging as well as discharging for a secondary one, by using a single composed of specific 1,3-dioxolane compound or its mixture with a solvent as the electrolytic solution. CONSTITUTION:The electrolytic solution is composed of 1,3-dioxolane (for example: 2-tetrafluoroethyl-4-pentafluoroethyl-1,3-dioxolane) alone with fluoroalkyl radicals at more than one position of 2, 5 and or its mixture with other solvent (for example: propylene carbonate), and more than one kind of solute (for example: lithim perchlorate) dissolved in the above solvent. This electrolytic solution 4 is used for a cell consisting of a positive electrode 1, a negative electrode 2 and a separator 3. This composition can improve not only discharging voltage for a primary cell, but also efficiency of charging as well as discharging for a secondary cell.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to primary and secondary batteries using organic electrolytes.

BACKGROUND OF THE INVENTION Organic electrolyte batteries are expected to have higher energy density than conventional batteries using aqueous solutions, and are being actively researched as secondary batteries and secondary batteries.

Among these, batteries that use lithium for the negative electrode and carbon fluoride, manganese dioxide, or copper oxide for the positive electrode have already been put into practical use as high-energy-density secondary batteries.

As the electrolyte for these organic electrolyte-secondary batteries, lithium perchlorate (LiCAO4), Houf, lithium nitride (
LiBF4) dissolved in propylene carbonate (PC) or γ-butyrolactone (γ-BL), or dissolved in a mixed solvent of PC and dimethoxyethane (DME) or PC and dioxolane (DiOx) have been put into practical use. Ta.

Recently, it has been reported that so-called synthetic metals such as titanium disulfide (TiS2), polyacetylene, polypyrrole, and polyaniline exhibit good characteristics as front surfaces for organic electrolyte secondary batteries.

On the other hand, in addition to the lithium surplus electrode, there are also electrodes that occlude lithium ions in the electrolyte when charged, and release them as lithium ions into the electrolyte when discharged, in addition to lithium surplus electrodes. Using polyacetylene and polyaniline, lithium ions in the electrolyte,
Occludes tetrabutylammonium ions by charging,
Electrostatic layers that emit electricity through discharge are being considered.

In addition to the same electrolyte as the primary battery mentioned above, the electrolyte for these secondary batteries includes 2-methyltetrahydrofuran as a solvent and lithium hexafluoroarsenate (LI) as a solute.
Combinations such as ASF6) + tetrabutylammonium perchlorate are being considered.

Problems to be Solved by the Invention Organic electrolyte batteries using negative electrodes and positive electrodes as described above have drawbacks such as low discharge voltage and low charge/discharge efficiency in secondary batteries. This is intended to improve these shortcomings.

Means for Solving the Problems The present invention provides an organic electrolyte battery using an electrolyte consisting of at least one organic solvent and at least one solute, in which the organic solvent is at least one at a position of 2.4°6.
1,3-dioxolane containing a fluoroalkyl group alone or a mixed solvent containing this as a component is used. Here, negative electrodes include synthetic metals such as fusible alloys, aluminum, and polyacetylene, which occlude kaions during charging in an electrolyte other than lithium and release them during discharge, and positive electrodes include metal oxides and metal calcosaponides. , fluorocarbon,
and polyacetylene, which absorbs anions in organic electrolytes when charged and releases them when discharged.

Synthetic metals such as polypyrrole and polyaniline are used.

The solutes that dissociate into anions and cations in the electrolyte include lithium salts such as lithium perchlorate, lithium borofluoride, and lithium hexabutyphosphate, and quaternary ammonium perchlorate salts such as tetrabutylammonium perchlorate. used. These solutes are mixed with 1,3-dioxolane having a fluoroalkyl group at at least one of the 2.4.5 positions, or with 1,3-dioxolane as a component and other components as PC, ethylene carbonate (Ice), γ-BL, DME.

One or a combination of two or more of DiOx, a-methyldioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran is used.

Effect 2.4.5 All 1,3-dioxolanes having a fluoroalkyl group in at least one position have a dielectric constant of 10.
The following is the lithium salt when this is used as a solvent,
The solubility of quaternary ammonium salt is higher than that of conventional PC or γ-BL.
small compared to

Furthermore, the electrical conductivity of the electrolytic solution in which the above solute is dissolved to a saturated state is approximately 2×10'Ω−1・α−1.
5X10 'Ω-'cm-' of electrolyte dissolved in c
, 1~1 compared to 1,4X10-2Ω-1・cIrL-1 of the electrolyte dissolved in a 1:1 mixed solvent of PC and DME.
It was two orders of magnitude lower and was thought to be inappropriate as an electrolyte for organic electrolyte batteries.

However, in low rate discharge, MnO2 and 0110
Metal oxides such as TiS2, Fe50, C
Batteries that use metal chalcogenides such as uFeS2, fluorocarbons, or synthetic metals such as polyacetylene and polypyrrole have higher discharge voltages than batteries that use conventional electrolytes, and secondary batteries have lower charging and discharging efficiency. improves. Furthermore, it was found that secondary batteries using polyacetylene or polyaniline as negative electrodes also showed improved charge/discharge efficiency, lowered the discharge voltage, and improved the characteristics of the negative electrode.

This is thought to be due to improved wetting of the electric current compared to conventional electrolyte threads using PC, γ-BL, or DME, but the detailed reason is not clear.

Furthermore, at least one of the 2, 4, and 5 positions has a fluoroalkyl group (-C:F5, -02F5, -CHF2).

-CH2F, -0H(CF3)2, CH2(
CFs), -CH2-CF3, etc., in which at least one or more hydrogens are substituted with fluorine) is added to 1,3-dioxolane having PC and other components. By using a mixed solvent containing γ-BL, DME, etc. as an electrolyte, the solubility of the solute increases and the electrical conductivity improves, so even in high rate discharge, the discharge is faster than when using a conventional electrolyte. Improvements in voltage and charge/discharge efficiency can be seen in secondary batteries.

The action and effect when using this 1,3-dioxolane having a fluoroalkyl group in an electrolytic solution are comparable to those when a fluorine-based surfactant is added to a conventional electrolytic solution.

Conventional fluorine fiber surfactants are made by bonding sulfonic acid or sulfonic acid ester to a linear or two-branched fluorinated alkyl group to make it hydrophilic or lipophilic. .

This is because a fluorinated alkyl group alone has no hydrophilicity or lipophilicity. Furthermore, the main functional difference between the present invention and the 1,3-dioxolane having a fluoroargyl group lies in the solubility of the solute. While conventional fluorine thread surfactants have no solute solubility, the 1,3-dioxolane having a fluoroalkyl group of the present invention has a solubility of about 0.01 to 0.2 mo/L/L. have sex. For this reason, the effects when used in batteries vary greatly as follows.

When using conventional fluorosurfactants.

At the stage when the electrolyte is injected into the battery, the surfactant acts on the positive and negative electrodes to wet them well, resulting in good contact between the positive and negative electrodes and the electrolyte, resulting in excellent battery performance. However, after the battery was prototyped and left unattended, the battery performance deteriorated.

This is because the surfactant gathers on the surface of the positive and negative electrodes, and because the surfactant itself does not have solubility for solutes, that is, it does not have ionic conductivity, it forms a kind of thin insulating film. This is probably because they are in the same state. The 1°3-dioxolane having a fluoroalkyl group of the present invention has solute solubility and conductivity of about 10-4Ω, and does not form an insulating film-like state even if it collects on the surface of the positive and negative electrodes. or because the basic chemical structure is dioxolane structure, it has affinity with other solvents such as PC+DME, γ-BL, and there is less collection of 1,3-dioxolane with fluoroalkyl group on the surface of the positive and negative electrodes. The battery exhibited stable and excellent performance even immediately after battery prototype production or after being left unused.

Example The present invention will be explained in detail below.

Example 1 Metallic lithium was used for the negative electrode, and fluorocarbon was used for the positive electrode active material. For the normal pupil, 100 parts by weight of fluorocarbon, 20 parts by weight of acetylene black as a conductive agent, and 10 parts by weight of polytetrafluoroethylene as a binder were added and mixed thoroughly to form a mixture. This mixture 0,
6g was buried in the mixture so that the titanium extracted band metal as a current collector was buried, and the size was 2cIrL x 2crr.
Press molded into L.

The mixture at the end of the positive electrode was removed, and a titanium ribbon serving as a lead was spot welded to the current collector. This positive theoretical capacitance is 332 mAh.

The negative electrode has a size of 2cW1×2CIn and a thickness of 0.2
It is made by crimping mn+ lithium onto a nickel net, and taking a lead from the edge of the net with a Nickefle ribbon, and has a theoretical electric capacity of 1600 mAh. Positive electrode above.

The negative (to) was placed in a battery case with a polypropylene nonwoven fabric as a separator interposed therebetween so that they were in close contact with each other. An electrolytic solution was added to this and vacuum impregnation was performed to impregnate the positive electrode mixture with the electrolytic solution.

A schematic diagram of this battery is shown in FIG. In the figure, 1 is a positive electrode, 2 is a negative electrode, 3 is a separator, 4 is an electrolytic solution, and 6 is a battery container.

For the electrolytic solution, 2-di(trifluoro)isopropyl-ethyl-1,3-dioxolane was used as the solvent of the present invention, and 0.2 mol/7i of L-CIOa was completely dissolved in this. Turning batteries into people. As a comparative example 1
γ-B with mol/β of LiClO4 dissolved! , B, 1,3-dioxolane with 1 moiv/1 Li
C is a battery using an electrolyte in which Cβ04 is dissolved. FIG. 2 shows the discharge curves of these batteries in 20'C1111A constant current discharge. As is clear from the figure, in low rate discharge, the discharge voltage is higher in case A using the electrolytic solution of the present invention.

Next, 1 has a fluoroalkyl ρ group at the 2.4.5 position.
．． We investigated which position of the fluoroalkyl group in 3-dioxolane is effective. 2.4 as an alkyl group, benCH2 0H2-CH2 tafluoroethyl group (-CFzCFs) 1
.

As a result of the same study as above with 3-dioxolane, 2
When 1°3-dioxolane having a fluoroalkyl group at the position was used, the discharge voltage and the utilization rate were better. In this case, the positions 4 and 6 are the same due to the symmetry of the molecule.

Next, we investigated the influence of the type of fluoroalkyl group. Using 1,3-dioxolane in which one hydrogen of CH2 at position 2 of 1,3-dioxolane was substituted with a fluoroalkyl group, the same study as above was conducted, and the result was -CFs<-CzFs<-CsF7> CaF9 It was noil. When a fluoroalkyl group becomes butyl,
The solute solubility of the solvent decreased, and the treasure performance decreased.

The effect on the number of fluorine atoms in the fluoroalkyl group was investigated. In this case, 1,3-dioxolane having an isopropyl fluoroalkyl group at the 2-position was investigated. The result is 05F6H)03F7≧05F5H2)
The order was C5F4H5 > 03F5H4, and the best case was when the alkyl group had one hydrogen and the rest were all fluorine.

In addition, in CH2 of 1,3-dioxolane, one hydrogen is substituted with a fluoroalkyl group, and two hydrogens are substituted with 2
As a result of examining the substitution of two fluoroalkyl groups, it was found that the one in which two hydrogen atoms were substituted with two fluoroalkyl groups had better performance when applied to a battery.

Example 2 A battery having the same configuration as Example 1 was used, except that only the electrolyte was changed. All solutes are F4 rather than L, and their concentration is 1 mol/2. peso volume% volume-tetrafluoroethyl/v-4
-Pentafluoroethyl/L'-1,3-dioxolane 6
A battery using a mixed solvent consisting of 0% by volume, peso
Volume % volume - E using a mixed solvent such as 50 volume % of 3-dioxolane, and as a comparative example, peso volume %
Volume - F, p using a mixed solvent from 60 volume %
A battery using a mixed solvent of c5° volume %, DMK 49.9 volume %, and Qj volume % of a commercially available fluorine thread surfactant is designated as G. Figure 3 shows the temperature of the battery at 20°C30 immediately after prototype production.
A discharge curve when mA constant current discharge is performed is shown. From this, good battery performance can be obtained by using 1,3-dioxolane having a fluoroalkyl group as a component of the solvent.

Figure 4 shows two batteries, D and G, which were left for 10 days after prototype production.
The discharge curve of 0°C 30mA discharge is shown. In the G battery,
Compared to the results shown in FIG. 3, the performance deteriorated considerably due to neglect. However, it can be seen that in the battery D of the present invention, there is almost no difference in performance.

In the above example, an example was shown in which fluorocarbon was used as the active material, but in addition to this, metal oxides such as MnO2 and CuO, and metal chalcogenides such as TiS2, FeS2, and CuFeS2 may be used. A similar effect was also seen.

In addition to secondary batteries, materials that occlude and release dilithium during charging and discharging, such as negative lithium, polyacetylene, polyparaphenylene, fusible alloys, and aluminum, are also used, such as TiS2, MnO2, and polyacetylene. , polypyrrole, polyparaphenylene, etc., can also be used as an electrolyte for secondary batteries.
, 3-dioxolane was effective.

In addition, LiC404 and LiBF4 are used as solutes in the electrolyte.
In addition, even when using lithium salts such as L-ASF6 and LiPF6, and quaternary ammonium salts such as tetraethylammonium perchlorate, it is better to use the 1,3-dioxolane having a fluoroalkyl group of the present invention. performance was achieved.

When using a mixed solvent containing 1,3-dioxolane as one component of the fluoroalkyl group of the present invention, other components other than the above-mentioned propylene carbonate include K, ethylene carbonate, γ-butyrolactone, dimethoxyethane, dioxolane, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, etc. can be used.

Effects of the Invention As described above, according to the present invention, the discharge voltage of an organic electrolyte secondary battery is improved, and the charging/discharging efficiency of a secondary battery is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of a battery according to an example of the present invention, and FIGS. 2, 3, and 4 are diagrams showing a comparison of discharge characteristics. 1... Positive, 2... Negative (to), 3...
... Separator, 4... Electrolyte. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Zuchiku 7'l'l (hp) Zeng Kaifall ""° Sokaida (Yukiyo)

Claims (1)

[Claims] 1,3-dioxolane having a fluoroalkyl group at at least one of the 2, 4, and 5 positions, or a mixed solvent containing 1,3-dioxolane as a component, and at least one dioxolane dissolved in the solvent.
An organic electrolyte battery with an electrolyte consisting of a species of solute.