JPS6035461A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To improve the preservation characteristic of an organic electrolyte battery by either adding a chelating agent, which can combine with metal existing in a positive active material to form a complex, to make the positive active material or dissolving said chelating agent in electrolyte. CONSTITUTION:In an organic electrolyte battery constituted by using Li as its negative electrode, a chelating agent such as phenanthroline which can combine with a metal contained in a positive active material to form a complex is added to make the positive active material. In another method, the chelating agent is dissolved in organic electrolyte. The chelating agen tends to dissolve in electrolyte or immediately combines with dissolved metallic ions to form a complex. Since the thus formed complex does not pass through a porous separator due to its large molecular size, any decrease in the characteristic of the battery which might be caused due to depositions formed on the negaitve electrode is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses metal oxides such as manganese dioxide, copper oxide, and lead oxide, and metal sulfides such as iron sulfide, copper sulfide, nickel sulfide, and molybdenum sulfide as positive electrode active materials. The negative electrode active materials include lithium, potassium, sodium, aluminum,
Light metals other than magnesium and alloys mainly composed of them are used, and esters such as propylene carbonate, ethylene carbonate, γ-butyrolactone, etc. are used as the electrolyte.
Tetrahydrofuran, 1,2-dimethoxyethane, 1.
An organic electrolyte battery that uses an inorganic salt such as lithium perchlorate, lithium borofluoride, or aluminum chloride dissolved in a single or mixed solvent of ether such as 3-dioxolane, especially when lithium is used for the negative electrode. Concerning improvements in organic electrolyte lithium batteries.

Structure of conventional examples and their problems Conventionally, positive electrodes for organic electrolyte lithium batteries have been made of metal compounds such as metal halides, oxides, and sulfides, solid active materials such as fluorocarbon, and liquids such as thionyl chloride and sulfuryl chloride. Active materials, gaseous active materials such as sulfur dioxide have been considered. Among these, solid active materials have attracted particular attention because of their ease of handling, and among them, lithium batteries using carbon fluoride, manganese dioxide, iron sulfide, and copper oxide as positive electrode active materials have already been put into practical use.

On the other hand, metal halides are excellent active materials due to their high energy density and high reactivity, but they have not been put into practical use at present due to their dissolution in electrolyte solutions and the magnitude of self-discharge in batteries. Not there.

However, metal oxides such as manganese dioxide and copper oxide to metal sulfides such as iron sulfide are not completely dissolved in the electrolyte, and during long-term storage of batteries, especially at high temperatures, electrolytic As dissolution progresses in the liquid, the dissolved metal ions pass through the separator and are deposited on the negative electrode lithium.
This results in deterioration of battery characteristics, such as an increase in the number of piles inside the battery.

Purpose of the Invention The present invention eliminates the above-mentioned disadvantages caused by the dissolution of metal oxides or metal sulfides of a positive electrode active material into an electrolytic solution, and provides an organic electrolyte battery with excellent storage characteristics. The purpose is to

Components of the Invention The present invention is characterized in that a chelating agent that forms a complex compound with a metal constituting a metal oxide or metal sulfide of a positive electrode active material is mixed into the positive electrode or dissolved in an electrolytic solution. Features. With this chelating agent, a complex compound is immediately formed with the ions of the metal that is about to be dissolved in the electrolytic solution or dissolved in the electrolytic solution. Since this complex compound has a much larger molecule than a metal ion, it can pass through a porous separator and can be prevented from being deposited on the negative electrode and deteriorating battery characteristics.

The chelating agent used here should be selected to be the one that is most compatible with the metal constituting the active material compound.
And when using the chelating agent dissolved in the electrolyte,
It goes without saying that the chelating agent must not react with the negative electrode metal such as lithium, but this is not the case when it is mixed into the positive electrode active material. However, when the chelating agent is mixed into the positive electrode active material, a larger amount of the chelating agent is required than when it is dissolved in the electrolyte.

Many chelating agents that form complex compounds with specific metals have been known, but there are only a limited number of chelating agents that do not react with lithium. Typical examples include phenanthroline, 272/-dipyridyl (bipyridine), and the like, which can be mixed into the positive electrode active material or dissolved into the electrolyte.

Note that when the present invention is applied to a battery that uses a metal halide with high solubility in the electrolyte as a positive electrode active material, self-discharge of the battery due to dissolution of this active material increases, and all of these dissolved metal ions are removed. A large amount of chelating agent is required to form a complex compound, which actually deteriorates the characteristics of the battery, making it unsuitable for batteries that use metal oxides or metal sulfides as positive electrode active materials, which have relatively low solubility. Particularly effective.

Description of Examples Example 1 Natural pyrite (Fed2) was purified as a positive electrode active material,
Pyrite powder with iron disulfide purity of about 96% is used.

This pyrite powder, acetylene black as a conductive material, and polytetrafluoroethylene as a binder were mixed in a weight ratio of 100:5:5, and 1 g of the mixture was pressure-molded on a nickel net to form a positive electrode. . The size of the electrode is 20x20mm.

The negative electrode used was a 0.2 g lithium sheet crimped onto a nickel net. The size of the electrode is 20X, same as the positive electrode.
Negative electrodes were placed on both sides of a 20 mm 0 positive i wrapped in polypropylene nonwoven fabric, and the mixture was placed in a polypropylene container, and propylene carbonate and 1,2-dimethoxyethane were mixed at a volume ratio of 1:1. 1 lithium perchlorate in the solvent
An electrolytic solution dissolved at a ratio of mol/β was injected and the cell was sealed to form a battery. Let's say this battery is a person.

Next, add 2 g of 7enanthroline to the same electrolyte as above,
B is a battery constructed in the same manner as the battery man using the electrolyte solution dissolved at a ratio of Q.

In addition, let C be a battery constructed in the same manner as Battery A by mixing 2% by weight of phenanthroline into the pyrite powder, which is the positive electrode active material. The characteristics of these batteries when discharged at a constant current of 4 m at 20°C are as follows. Shown in Figure 1.

As is clear from FIG. 1, both batteries i and tz (1, 1) exhibit nearly the same characteristics.

Next, batteries A', which have the same configuration as battery groups B and C, respectively,
A": B', B": C'l 0% (-+ri.

Batteries /, B/, and C/ were stored at 60°C for 6 months to batteries A'', B'', and C'' were stored at 60'C for 12 months at 20°C. Discharge was performed at a constant current of 4 mA.

The results are shown in Figure 2. The internal resistance of these batteries immediately after manufacture and after storage is shown in the table below.

As is clear from Figure 2, even when batteries C or B containing the chelating agent phenanthroline in the positive electrode active material or electrolyte are stored at 60°C, the voltage at the initial stage of discharge decreases slightly. However, almost no deterioration of characteristics was observed.

On the other hand, battery A which does not contain any chelating agent
During high-temperature storage, iron disulfide, which is the positive electrode active material, dissolves in the electrolyte, and iron further precipitates on the negative electrode lithium, which increases the internal resistance of the battery as shown in the table. As the period becomes longer, a decrease in discharge voltage is observed.

1. These effects can be obtained not only when phenanthroline is used, but also when a chelating agent that forms a complex with the metal constituting the positive electrode active material compound is appropriately selected. For example, a similar effect was obtained when 2,2'-dipyridyl was mixed.

Example 2 Next, copper oxide (Cub) is used as a positive electrode active material.

In this case as well, a battery was constructed in the same manner as in Example 1. That is, copper oxide powder, acetylene black, and polytetrafluoroethylene were mixed in a weight ratio of 100:5:6.
1 g of it was pressure molded onto a nickel net. A positive electrode with a size of 20 x 20 mm is used. A 0.2 g lithium sheet is used as a negative electrode with a size of 2 x 20 mm.
It was crimped onto a nickel net of mm in diameter and placed on both sides of a positive electrode wrapped in a nonwoven fabric made of polypropylene.

These were assembled in a polypropylene container, and lithium perchlorate was added in a solvent containing 1 mole/1 mole of propylene carbonate and 1,2-dimethoxyethane mixed in a volume ratio of 1.
An electrolyte solution dissolved at a ratio of β was injected and sealed to form a battery. These batteries are designated as DI and D'.

Next, batteries using 2 g/l (0 ratio) of 2,2'-dipyridyl dissolved in the electrolyte were prepared as E, E' and 17.
A battery in which 2,2'~dipyridyl of 2 parts by weight is mixed into the copper oxide powder of the positive electrode active material is called F,? '.

Immediately after manufacturing batteries D, E, and F, batteries n/, y,′,
After storing F/ at 60℃ for 12 months, each was heated to 4m at 20℃.
Figure 3 shows the characteristics when discharging at a constant current of A.

As is clear from Fig. 3, batteries E and F have almost the same characteristics, and batteries E/ and F/ are also similar to battery E.
, while there is almost no characteristic deterioration compared to F,
Battery D' has a lower voltage at the beginning of discharge.

When copper oxide is used as the positive electrode active material, this is not as great as when pyrite is used as the active material, but during high-temperature storage, oxidized steel gradually dissolves in the electrolyte, and copper is deposited on the negative electrode lithium surface, causing the battery The result is that the internal resistance of the battery increases, causing a delay in the rise of the voltage at the start of discharge.

On the other hand, batteries E' and F' are chelating agents 2,
The incorporation of 2'-dipyridyl forms a complex compound with dissolved copper ions, preventing copper ions from being deposited on the negative electrode lithium, and shows almost no deterioration in properties even after long-term high-temperature storage.

Various studies have been carried out regarding the optimum amount of the chelating agent to be added, but the ratio that gives the best effect on average is 0.006 mol to 0.05 mol per 11 mol of the electrolytic solution when dissolved in the electrolytic solution. However, when mixed into the positive electrode active material, the optimal range was 0.2% to 2% by weight relative to the active material.

Effects of the Invention As described above, according to the present invention, the long-term storage, particularly the long-term storage characteristics at high temperatures, of an organic electrolyte battery using a metal oxide or metal sulfide as an active material can be improved.

[Brief explanation of the drawing]

Figure 1 compares the initial characteristics of iron disulfide-lithium batteries, Figure 2 compares the characteristics after storage, and Figure 3 compares the initial and storage characteristics of copper oxide-1notium batteries. This is a diagram. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2: Discharge time (needle S) Figure 2: Discharge time (light IS) Figure 3: Between discharge legs (IS)

Claims (1)

[Claims] It has a positive electrode using a metal oxide or sulfide as an active material, a negative electrode using a light metal as an active material, and an organic electrolyte, and forms a complex compound with the metal constituting the positive electrode active material in the positive electrode or electrolyte. An organic electrolyte battery characterized in that it contains or dissolves a quenching agent.