JPS5856466B2 - dench - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that the active material of the negative electrode is an alkali metal, preferably lithium, and the positive electrode is made of copper oxide, silver chromate, a fluorinated hydrocarbon polymer, or a combination of the fluorinated hydrocarbon polymer and the above. The present invention relates to high energy density batteries comprising depolarizers selected from mixtures with metal compounds.

Commonly used depolarizers include copper oxide, iron oxide, copper sulfide, iron sulfide, silver chromate, lead chromate, polymerized fluorinated hydrocarbons, and mixtures of fluorinated hydrocarbons and the metal compounds mentioned above. etc. can be mentioned.

Such a system is already known, and consists of an electrolytic solution consisting of lithium perchlorate or lithium fluoroborate as a solute and one or more neutral organic solvents with high dissolving power as a solvent. are also known in combination with the above depolarizers.

It is generally known that the smaller the internal resistance of a battery, the higher the rate of discharge.

Therefore, in order to increase the average voltage of the battery, the resistance of the electrolyte, which forms part of the internal resistance of the battery, must be made as small as possible.

The capacity of a battery depends on the conductivity of the electrolyte as well as its ability to dissolve the discharge products so that no polarization occurs at the electrodes.

Therefore, a high dissolving power makes it possible, on the one hand, to dissolve a sufficient amount of solute so that a high conductivity is obtained, and on the other hand, to dissolve the discharge products of the lithium electrode, thereby preventing polarization.

Conventional solvents were preferably chosen among saturated ethers.

The solvency power of the ether is due to the fact that it is saturated and partly due to the presence of an oxygen atom with at least one free electron pair.

U.S. Pat. No. 3,542,601 describes tetrahydrofuran, tetrahydropyran and 4,4-dimethyl-1,3-dioxane as such electrolyte solvents.

In this regard, the addition of a second solvent, specifically to tetrahydrofuran, is described in U.S. Pat.
, 511,716, and the same patent No. 3゜70L688 suggests addition of 1,1- or 1,2-dimethoxyethane and various other solvents to tetrahydrofuran. has been done.

It has been found that the dissolving power of a cyclic ether such as tetrahydrofuran or an aliphatic ether such as dimethoxyethane increases as the number of oxygen atoms (No) increases relative to the number of carbon atoms (Nc) in the molecule.

According to this fact, the preferred solvent is dioxolane, which has two oxygen atoms but 4,4-dimethyl-1
, 3-dioxane (which has two oxygen atoms).

Furthermore, when selecting a solvent for the electrolytic solution, it is also an important condition that the difference between the concentration at which the electrolytic solution exhibits the highest conductive dust and the saturation point of dissolution is large.

For example, no matter how high the concentration of conductive dust in the electrolytic solution is, if the saturation point is close to the concentration at which the maximum conductivity occurs, it cannot be used at this concentration.

This is because the discharge products dissolved in the electrolytic solution reach a saturation point before the end of the discharge, and the lithium electrode becomes polarized and the discharge stops.

It is therefore advantageous for the maximum conductivity to be obtained at as low a solute concentration as possible.

This is also advantageous since solutes are expensive.

In fact, as is clear from the graph below, dioxolane has the characteristics as a solvent for the electrolyte of such batteries, namely, the maximum conductivity is large, the maximum conductivity can be obtained at a low concentration, and the saturation point ( (equivalent to the end point of the conductivity recurve) has a large difference from the concentration at which the maximum conductivity occurs.

However, a dioxolane solution of lithium perchlorate is used as the electrolyte in lithium batteries that use metallic lithium as the negative electrode active material and metal sulfides or metal fluorides such as iron, copper, or nickel as the positive electrode active material. In these batteries, gas is generated due to the electrochemical reaction, and the amount of gas generated can reach 36 times the volume of the battery, which is a serious drawback as a battery.

In contrast, the inventors have found that copper oxide, silver chromate, fluorinated hydrocarbon polymers, and mixtures of these fluorinated hydrocarbon polymers and these metal compounds are used as positive electrode active materials in lithium batteries. Even if dioxolane is used as a solvent for the electrolyte, no gas is generated;
It was discovered that the advantages of dioxolane described above can be effectively utilized, leading to the present invention.

It is therefore an object of the present invention to provide a negative electrode whose active substance is lithium, a group in which the active substance is copper oxide, silver chromate, a fluorinated hydrocarbon polymer and a mixture of a fluorinated hydrocarbon polymer and said metal compound. An object of the present invention is to provide a battery comprising a positive electrode made of a depolarizer selected from the following, and an electrolytic solution made of a solute and a solvent, the solvent of the electrolytic solution being dioxolane.

According to a preferred embodiment, the solute is lithium perchlorate in a concentration range of 1 to 2.5 molar.

The characteristics of the present invention will be clarified with reference to the accompanying drawings.

In Figure 1, the concentration of lithium perchlorate (mol/l) in the dioxolane solution is plotted on the horizontal axis, and the conductive dust (10-3
Ω-1 cm-1) is plotted on the vertical axis.

Measurements were performed at 20°C. This solvent is approximately 3.6 mol/l
It shows a maximum conductivity of about 10 Ω cm and can dissolve up to about 4.2 moles of lithium perchlorate per 11 (saturation point).
.

On the other hand, according to US Pat. No. 3,542,601, tetrahydrofuran has a maximum conductivity of about 610-3 Ω-1 cm 1 at about 2 mol/l, and a saturation point of 2
．． It is 5 mol/l.

Therefore, if used at a concentration of 2 mol/l, dioxolane has an electrical conductivity of about 7.510-3 Ω-1 cm-1, which is higher and more advantageous than tetrahydrofuran, and it is also advantageous in terms of the difference from the saturation point. be.

FIG. 2 shows a discharge curve in a lithium-copper oxide battery using an electrolytic solution containing dioxolane as a solvent.

The batteries used in the discharge experiments were button-shaped.

This battery consists of two lithium negative electrodes with a thickness of 1.2 mm, two
It consists of one positive electrode with a thickness of mm and a separator with a thickness of 0.2 mm, and 2 ml of electrolyte is injected.

The electrochemical active range is 10 crB.

The positive electrode active material of the battery exhibiting the discharge curve of FIG. 2 is copper oxide.

Specifically, the positive electrode contains 77% copper oxide and 7.7% graphite.
and 15.3% binder.

The concentration of lithium perchlorate in the electrolyte is 1.5 molar.

The cell was discharged through a 100 ohm resistor.

This is the average output current density of 1 mA/c, i.e. 10
Corresponds to a current of rnA.

In this case, it can be seen that the discharge is stable for a long time.

The theoretical capacity of the battery is 1.4Ah, but in reality it is 1.2Ah.
It was Ah.

FIG. 3 shows the discharge curve of a lithium-silver chromate battery whose electrolyte contained dioxolane was discharged through a 300 ohm resistance.

This cell is of the same type and construction as the cell described above, but uses the same proportion of silver chromate instead of copper oxide.

The discharge of this battery ends at 2 volts.

Figure 4 shows that the positive electrode is polytetrafluoroethylene (PTF).
E) 1 g of cotton, a mixture of 85% (by weight), 15% graphite and 25% camphor (used as pore-forming agent and subsequently removed by heating), the electrolyte being 1.5 mol lithium perchlorate; 2 shows a discharge curve when a battery made of a dioxolane solution containing .

Figure 5 shows that the anode is polytetrafluoroethylene 15.3
%, 77% Cu and 7.7% graphite, and the electrolyte was 1.5% lithium perchlorate.
Figure 2 shows the discharge curve of a battery with a lithium anode and a dioxolane solution containing mol of dioxolane discharged through a resistance of 50 ohms.

The obtained results are plotted as voltage (volt) on the vertical axis and discharge time (
time) is plotted on the horizontal axis and shown as the above curve.

The capacity of the battery shown in Figure 4 is approximately 0.55A at an average current of 12mA.
It is h.

The capacity of the cell of FIG. 5 was about 1.6 Ah compared to the actual capacity of CuO of about 1.4 Ah.

In each of the above-mentioned batteries, no gas generation was observed in the electrochemical reaction even when dioxolane was used as a solvent for the electrolyte.

[Brief explanation of the drawing]

Figure 1 shows the concentration of lithium perchlorate (mol/l) in dioxolane solution versus conductive dust (10-”Ω-1c).
The graph plotting m( ) and FIGS. 2 to 5 are graphs showing discharge curves of various lithium batteries using dioxolane as a solvent for the electrolytic solution.

Claims (1)

[Claims] 1. A negative electrode whose active substance is lithium, and a depolarizer whose active substance is selected from the group consisting of copper oxide, silver chromate, a fluorinated hydrocarbon polymer, and a mixture of this fluorinated hydrocarbon polymer and the metal compound mentioned above. 1. A battery comprising: a positive electrode consisting of; and an electrolytic solution consisting of a solute and a solvent, wherein the solvent of the electrolytic solution is dioxolane.