JPH10312813A - Organic electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a storage characteristic of a battery by adding a reaction inhibitor in an organic electrolyte to check reaction of a manganese dioxide with an electrolyte. SOLUTION: A battery uses a manganese dioxide as a positive electrode active material, and normally uses a propylene carbonate as an organic electrolyte. A substance used as a reaction inhibitor to be added to this electrolyte is desirable to be a polyacrylamide (acrylamide-acrylic acid copolymer), and non-electric charge polyacrylamide or the like is cited as its representative one. Reactivity of the manganese dioxide to the electrolyte reduces by adding this in the electrolyte. This is caused by the fact that the activity of a manganese dioxide surface on the basis of sticking water, joining water, a surface functional group or the like deteriorates because a comparatively stable adsorbing layer is formed in an active part of the manganese dioxide surface by adding the reaction inhibitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic electrolyte battery using an alkali metal such as lithium as a negative electrode active material and manganese dioxide as a positive electrode active material, and more particularly to an improvement in an electrolyte solution.

[0002]

2. Description of the Related Art In an organic electrolyte battery, an alkali metal such as lithium is used as a negative electrode active material, manganese dioxide is used as a positive electrode active material, and propylene carbonate is used as an electrolyte.
LiClO ₄ , LiPF ₆ , LiAsF ₆ , L can be added to an organic solvent such as 2-dimethoxyethane or 1,3-dioxolan.
An electrolyte in which one or more electrolytes such as iSbF ₆ and LiB (C ₆ H ₅ ) ₄ are dissolved is used. Among these organic solvents, especially propylene carbonate is
It is widely used because it has a high dielectric constant, can dissolve the electrolyte at a high concentration, and has a wide use temperature range.

[0003] When manganese dioxide is used as the positive electrode active material of the above battery, manganese dioxide adheres to the surface of water. Since it has bound water and surface functional groups, its surface activity is high, which causes a potential higher than the theoretical potential when a battery is formed. Further, when an organic solvent having a cyclic ester bond such as the propylene carbonate is used as the electrolyte solvent, manganese dioxide and propylene carbonate react during storage, and propylene carbonate is oxidized and decomposed, so that the inside of the battery is removed. Carbon dioxide (CO
₂ ) occurs, causing a decrease in battery performance such as an increase in the total battery height and an increase in internal impedance.

On the other hand, there has been proposed a method for preventing the decomposition of propylene carbonate by performing a preliminary discharge immediately after the production of the battery (Japanese Patent Laid-Open No. 55-80276). It must be discharged to a predetermined voltage, which requires a great deal of work industrially.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and in an organic electrolyte battery using manganese dioxide as a positive electrode active material, manganese dioxide reacts with the electrolyte to improve battery performance. An object of the present invention is to provide a battery in which the electrolytic solution is improved so as not to be deteriorated, and the storage characteristics are not deteriorated even if a preliminary discharge is not performed immediately after manufacturing the battery as in the related art.

[0006]

According to the present invention, the above object has been achieved by adding a reaction inhibitor for preventing the reaction between manganese dioxide and the electrolyte in the electrolyte.
That is, the present invention uses an alkali metal as a negative electrode active material,
Manganese dioxide as a positive electrode active material, in an organic electrolyte battery comprising an organic electrolyte, characterized in that a reaction inhibitor for inhibiting the reaction between manganese dioxide and the electrolyte is added to the organic electrolyte. I do.

In the present invention, the substance used as the reaction inhibitor is preferably polyacrylamide (acrylamide-acrylic acid copolymer). Representative examples thereof include uncharged polyacrylamide (PAM) and charged polyacrylamide (anionic hydrolysis). Polyacrylamide (HPAM)).

In the present invention, the reactivity of manganese dioxide with respect to an electrolyte containing propylene carbonate or the like is reduced by adding a reaction inhibitor to the electrolyte as described above. Although the reason for the decrease in reactivity is not always clear at present, the addition of a blocking agent results in the formation of a relatively stable adsorption layer on the active site on the surface of manganese dioxide. It is considered that the activity of the surface of manganese dioxide based on such factors is reduced.

In the battery of the present invention, as the negative electrode active material,
For example, alkali metals such as lithium, sodium, and potassium are used. The negative electrode may be composed of the alkali metal itself, but may be composed of an alloy such as a lithium alloy.

When a negative electrode is made of this lithium alloy, lithium acts as a negative electrode active material. Examples of the above lithium alloy include lithium-aluminum alloy, lithium-silicon alloy, lithium-tin alloy, lithium-lead alloy, lithium-antimony alloy, lithium-indium alloy, lithium-gallium alloy, and lithium-bismuth alloy. , Lithium-germanium alloy,
Lithium-indium-gallium alloy and the like can be mentioned. In addition, a material obtained by further adding a small amount of another metal to the above lithium alloy can be used for the negative electrode.

[0011] The organic electrolyte solution is usually an electrolyte solvent composed of propylene carbonate or an organic solvent containing ethylene carbonate, γ-butyrolactone, etc. having a cyclic ester bond similar to propylene carbonate.
_{O 4, LiPF 6, LiAsF 6} , LiSbF 6, Li
An electrolyte in which one or more electrolytes such as B (C ₆ H ₅ ) ₄ are dissolved is used. The above-mentioned propylene carbonate, ethylene carbonate, γ-butyrolactone and the like may be used alone as an electrolyte solvent.
An electrolytic solution is prepared by mixing them or mixing them with an organic solvent such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3-dioxolan. It may be used as a solvent.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. (Example) A battery shown in FIG. 1 was manufactured by assembling a battery according to a conventional method. In FIG. 1, reference numeral 2 denotes a negative electrode made of lithium, and this negative electrode 2 is a negative electrode can 3 made of stainless steel.
A negative electrode current collector 4 composed of a stainless steel mesh spot-welded in advance to the inner surface of the negative electrode has a diameter of 16 mm and a thickness of 0.1 mm.
It is formed by compressing a 2 mm lithium plate. 5
Is a separator made of a microporous polypropylene film, and 6 is a positive electrode obtained by press-molding a positive electrode mixture containing manganese dioxide as a positive electrode active material, and was produced as follows.

That is, manganese dioxide heat-treated at a temperature in the range of 350 to 450 ° C. is used as an active material, and the manganese dioxide, carbon powder as a conductive agent, and fluororesin powder as a binder are mixed at 85:10: 5 and then press-molded the mixture,
Heat treatment was performed at 350 ° C. to produce a disk-shaped compact having a diameter of 16 mm and a thickness of 0.6 mm.

Further, in FIG. 1, reference numeral 7 denotes a positive electrode current collector made of a stainless steel net disposed on one side of the positive electrode 6 when the positive electrode 6 is subjected to pressure molding. Reference numeral 8 denotes a stainless steel positive electrode can, and reference numeral 9 denotes an annular gasket made of polypropylene.

In this battery, lithium perchlorate (LiClO ₄ ) is mixed with a mixed solvent of propylene carbonate and 1,2-dimethoxyethane at a volume ratio of 2: 1 as an organic electrolyte.
Was dissolved at 1 mol / l, and 1 g / l of polyacrylamide was further dissolved and used as a reaction inhibitor in this electrolytic solution. The battery is a coin-shaped battery having a diameter of 20.0 mm.

(Comparative Example 1) A battery was manufactured in the same manner as in the above Example except that no reaction inhibitor was added to the electrolytic solution.

The following three tests were conducted on the battery of the above-described embodiment and the battery of Comparative Example 1. First, 10 batteries of each of the above Example and Comparative Example 1 were stored at 80 ° C. for 48 hours, and an increase in the total battery height due to storage was examined. The total battery height before storage was within the range of 1.52 ± 0.02 mm for all batteries, and those whose total battery height exceeded 1.56 mm due to storage were regarded as defective in total height. Was. The denominator of the numerical values in Table 1 indicates the number of batteries subjected to the test, and the numerator indicates the number of batteries in which the total height failure occurred.

[0018]

[Table 1]

As shown in Table 1, in the battery of Comparative Example 1 in which no additive was added to the electrolytic solution, all the batteries subjected to the test had a total height failure due to storage. No defect of the total height occurred at all in the battery. Next, the internal impedance of the battery after high-temperature storage was measured at a frequency of 1 kHz. The results are shown in Table 2 below.

[0020]

[Table 2]

From Table 2, it can be seen that the internal impedance of the battery of Comparative Example 1 significantly increased after storage, whereas the internal impedance of the battery of Example 1 of the present invention increased only slightly after storage.

(Comparative Example 2) The battery manufactured in Comparative Example 1 was
Immediately after the production of the battery, a pre-discharge was performed to 3.2 V to remove a high potential portion, thereby suppressing the reaction between manganese dioxide and propylene carbonate. This battery is referred to as Comparative Example 2.

With respect to the battery of the above embodiment and the battery of Comparative Example 2, the discharge end voltage was 2.5 V at 25 ° C. and a resistance of 15 kΩ.
The discharge duration time when the battery was continuously discharged until the discharge was measured. Table 3 shows the results.

[0024]

[Table 3]

As shown in Table 3, the batteries of Examples had a longer discharge time than the batteries of Comparative Example 2 which had been pre-discharged, and a decrease in discharge capacity due to the addition of additives to the electrolyte was observed. Did not.

[0026]

As described above, in the organic electrolyte battery of the present invention, the reaction between manganese dioxide, which is a positive electrode active material, and manganese dioxide can be prevented by adding a reaction inhibitor to the electrolyte. The storage characteristics of the battery. Further, the present invention can improve the productivity as compared with the conventional method of preventing the decomposition of propylene carbonate by the preliminary discharge.

[Brief description of the drawings]

FIG. 1 is a sectional view of a battery according to an embodiment of the present invention.

[Description of Signs] 1 ... Battery, 2 ... Negative electrode active material, 3 ... Negative electrode can, 4 ... Negative electrode current collector, 5 ... Separator, 6 ... Positive electrode active material, 7 ... Positive electrode current collector, 8 ... Positive electrode can, 9 …gasket.

Claims (2)

[Claims] 1. An organic electrolyte battery comprising an alkali metal as a negative electrode active material, manganese dioxide as a positive electrode active material, and an organic electrolyte, wherein the reaction between the manganese dioxide and the electrolyte in the organic electrolyte is prevented. An organic electrolyte battery, wherein a reaction inhibitor is added. 2. The organic electrolyte battery according to claim 1, wherein the reaction inhibitor is polyacrylamide.