JPS61135056A - Manufacture of organic electrolyte cell - Google Patents

Abstract

PURPOSE:To improve storage property of a cell in a high temperature and a high humidity, by heat-treating copric oxide in a nitrogen gas atmosphere, replacing with nitrogen gas while returning to a normal air pressure, and then mixing with a chalcopyrite to make up a positive electrode substance. CONSTITUTION:To avoid a temporary drop of voltage in an initial discharge phase, in an organic electrolyte battery with a positive electrode 4 of copric oxide and a negative electrode 2 of lithium, a mixture of copric oxide and chalcopyrite is used for the positive electrode 4. In this case, the copric oxide is heat-treated in a nitrogen atmosphere, replaced with nitrogen gas while returning to the atmospheric pressure, to make a main active substance, and chalcopyrite is mixed as the secondary active substance, to make up the positive electrode 4. Therefore, absorbed oxygen to the copric oxide is almost all removed, separation of the melted ferric oxide on the negative electrode from the chalcopyrite in a long period storage is prevented, and an extensive improvement of storage property can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the production of organic electrolyte batteries using a mixture of cupric oxide and chalcopyrite as a positive electrode active material and lithium or a lithium-based alloy as a negative electrode. Concerning improvements in law.

BACKGROUND OF THE INVENTION Conventionally, so-called 3V class lithium batteries have been put into practical use as organic electrolyte batteries, using carbon fluoride, manganese dioxide, thionychloride, sulfur dioxide, etc. as positive electrode active materials.

In contrast, recently, organic electrolyte batteries have excellent storage properties,
Focusing on leakage resistance, attempts are being made to develop so-called 1.5v class lithium batteries that are directly compatible with silver oxide batteries, alkaline manganese batteries, etc. used in precision electronic devices such as electronic watches.

This type of battery uses cupric oxide as the positive electrode active material.

Lithium batteries using disulfide, bismuth oxide, lead bismuth oxide, etc. are already known, and among them, cupric oxide/lithium batteries are the most promising battery system because of their large capacity and good storage characteristics. I can say that there is.

Problems to be Solved by the Invention However, this battery system has a drawback in the discharge characteristics of the battery, particularly in that the voltage temporarily drops before the voltage settles to a constant value at the beginning of discharge. This phenomenon becomes an important problem especially when used in precision electronic equipment such as electronic watches.

This voltage drop phenomenon is unique to cupric oxide/lithium batteries, and cannot be resolved even if the electrolyte is changed.

Therefore, one measure to eliminate this drop in voltage is to mix an active material with a higher discharge voltage than cupric oxide with cupric oxide, and to preferentially use the mixed active material in the early stage of battery discharge. It is possible to eliminate the voltage drop phenomenon by causing the reaction to occur.

In this case, it goes without saying that the active material to be mixed must not react with cupric oxide, but in order to prevent the discharge voltage of the battery from becoming two-stage, the active material and the lithium negative electrode must be compatible. It is desirable that the discharge voltage of the combined battery is equal to, but slightly higher than, the discharge voltage of the cupric oxide/lithium battery. At the same time, the active material must have a large theoretical capacitance.

JP-A-58-206056 mentions chalcobyrite as the active material to be mixed.

Approximately 1.4 for the combination of cupric oxide positive electrode and lithium negative electrode
In contrast, the combination of chalcopyrite positive electrode and lithium negative electrode shows a discharge voltage of approximately 1.6 V, with a voltage drop at the beginning of discharge. is also not accepted. However, the energy density per weight of cupric oxide is ay 3mAh/g, while chalcopyrite is 544-584f
f1Ah/, 9, and the discharge capacity is larger when cupric oxide is used.

Therefore, by mixing appropriate amounts of these cupric oxides and chalcobyrite, it is possible to obtain a battery with a discharge voltage of 1.4 to 1.6V, no drop in voltage at the initial stage of discharge, and a relatively large discharge capacity. can.

Among the 1.5V class lithium batteries that have been proposed so far, it can be said that this battery system that combines lithium with a mixed active material of cupric oxide and chalcopyrite is the best. There is one problem when using it as a practical battery.

Normally, these 1.6v class lithium batteries take advantage of the characteristics of lithium batteries, such as low self-discharge and excellent leakage resistance, and are intended to be used as power sources for electronic watches, small calculators, etc. that operate for long periods with low current consumption. It is something. Therefore, the storage characteristics of the battery regarding self-discharge of the battery are important requirements.

On the other hand, cupric oxide, which is the main active material, is a substance usually obtained by heating copper nitrate, copper carbonate, copper hydroxide, etc. in air at a temperature of about 70,000 °C. Similarly, cuprous oxide (C
A method of heating u20) in air or oxygen gas is also known.

In any case, the resulting copper oxide is not 100% cupric oxide, but contains a slight amount of cuprous oxide.

Of course, this is hardly a problem in terms of the electrical characteristics of the battery. However, it is well known that cuprous oxide adsorbs oxygen (02,O-) on its surface more easily than cupric oxide, and both cuprous oxide and cupric oxide are highly catalytic. It is also well known that it is a powerful substance. This means that when cupric oxide is used alone as a cathode active material, there is no Hd, but when chalcopyrite is used in combination as an opening material, especially in the presence of a trace amount of water, the catalytic action of copper oxide and the above-mentioned Chalcopyrite is partially decomposed by the adsorbed oxygen, and iron oxide (Fe2O2) is generated on the surface.

As a result, when a battery is stored for a long time, especially in a humid environment, iron oxide dissolves in the electrolyte and is deposited on the negative electrode lithium through the separator, causing a micro short circuit in the battery, resulting in a decrease in battery voltage and discharge electricity. In some cases, the problem of volume reduction occurred. This tendency is particularly noticeable during storage under high temperature and humidity.

When this battery is used in electronic watches or small calculators that require a high degree of reliability, a drop in battery voltage, discharge, and a drop in the amount of electricity become a major problem.

An object of the present invention is to improve the storage characteristics of a battery whose positive electrode active material is a mixture of cupric oxide, which is the main active material, and chalcopyrite, which is the sub-active material.

Means to Solve the Problems The present invention provides a battery in which a mixture of cupric oxide and chalcopyrite is used as the positive electrode active material and lithium is used as the negative electrode. It is characterized by performing heat treatment in a vacuum chamber or heat treatment under reduced pressure, purging with nitrogen gas or inert gas, and returning to normal pressure.

In a battery that uses a mixture of cupric oxide and chalcopyrite as a positive electrode active material, as mentioned above, during long-term storage, especially long-term storage under high temperature and humidity, iron oxide generated from chalcopyrite dissolves and forms a negative electrode. precipitation, micro short circuit,
The phenomenon of capacity reduction is observed in some cases, which is a problem.

The amount of chalcopyrite to be mixed with cupric oxide, which is the main active material, is appropriate from 2Q to 40% by weight of the total active material, considering the discharge voltage characteristics and electric capacity of the battery. When a large amount of chalcopyrite is mixed, precipitation of iron on the negative electrode is noticeable.

As mentioned above, this is caused by three factors: the catalytic properties of cupric oxide, oxygen adsorbed by cupric oxide (including some cuprous oxide), and moisture entering the battery from outside. It is thought that there is an interaction.

Reducing the catalytic properties of cupric oxide may lead to a decline in battery characteristics, and to prevent moisture from entering from the outside, small batteries, such as those used as power sources for electronic watches, require a resin crimp seal method. The above is considered to be unavoidable.

Therefore, it is considered that the most effective means for preventing the deterioration of storage characteristics of a battery is to reduce or eliminate oxygen adsorbed to cupric oxide (partly containing cuprous oxide).

The present inventors have demonstrated that cupric oxide can be oxidized by heat treatment in a nitrogen gas or inert gas atmosphere or under reduced pressure, and by replacing the cupric oxide with nitrogen gas or inert gas when returning to atmospheric pressure. It has been found that most of the oxygen adsorbed on copper can be removed, resulting in good storage characteristics of the battery.

The temperature for the heat treatment here is preferably in the range of 80 to 350°C; if the temperature is lower than this, it will take a long time to remove the adsorbed oxygen, and if the temperature is higher than this, the oxidation process will take place. Partial decomposition of dicopper begins, which is undesirable.

Example The details of the present invention will be explained below using Examples.

(Example 1) Cupric oxide and chalcopyrite were mixed in various ratios,
This was mixed with acetylene black as a conductive material and an aqueous dispersion of a copolymer of tetrafluoroethylene and 67-propylene as a binder, and after drying, the diameter was 8.5 mm.
It was press-molded into a disk shape with a thickness of 0.7 mm and a positive electrode.

Mixing ratio of cupric oxide and chalcopyrite.

Table 1 shows the amount of conductive material, the amount of binder, and the theoretical amount of electricity charged in the active material at that time.

In Table 1, A-F are those using cupric oxide as is, (
In A') to (F'), cupric oxide was heated at 100° C. for 6 hours under a reduced pressure of 6 annHg or less, and then nitrogen gas was passed through it to return the pressure to atmospheric pressure.

A button-shaped battery shown in FIG. 1 was constructed using these positive electrodes. In Fig. 1, numeral 1 is a sealing plate made of nickel-plated stainless steel, and its inner surface has a diameter of 6 mm.
7. Negative FM2 made of metallic lithium with a thickness of 0.7 mm
is crimped. The theoretical capacitance of the negative electrode is 50 mAh.

3 is a polypropylene separator containing propylene carbonate and 1.2 dimethoxyethane in a volume ratio of 1:1.
Add 1 mo/L of lithium perchlorate to the solvent mixed in the ratio of
It is impregnated with an electrolytic solution dissolved at a ratio of //71.

Reference numeral 4 denotes the disk-shaped positive electrode described above, which is further pressure-molded within a nickel-plated iron battery case 6. 6 is a gasket made of polypropylene. The dimensions of the completed battery are 9.5 ff in diameter and 2-01111 in height. The theoretical amount of electricity charged in the positive electrode is as shown in Table 1.

These batteries A-F, and (A') to (F') at 20°
Figure 2 shows the characteristics when discharging at C with a load of 30Ω. Still battery M~F, (A')~(F') 6
After storage for 6 months at 0'C and 90% humidity, 20°
FIG. 3 shows the characteristics of batteries A to F when discharged under a load of 30 Ω at C, and FIG. 4 shows the characteristics of batteries (A') to (F'), respectively.

As is clear from Figure 2, the initial battery characteristics are completely unrelated to the presence or absence of heat treatment of cupric oxide, and as the mixing ratio of chalcopyrite increases, the use of cupric oxide alone as an active material increases. When using this method, the drop in voltage at the initial stage of discharge is eliminated.

That is, a mixture of 20% or more chalcopyrite (C-
No drop in voltage was observed in F and (C') to (F')). However, 60% mixture (F and (
F')1'i, it takes a relatively long time until the voltage becomes flat. This is not preferable when used as a power source for precision equipment such as an electronic watch. Therefore, the desirable mixing ratio of chalcopyrite is 20% to 40%.

As is clear from FIG. 3, when stored at high temperature and high humidity, the higher the mixing ratio of chalcopyrite in the positive electrode active material, the more significant the decrease in the discharge voltage and the amount of discharged electricity. This is thought to be because, as mentioned above, the greater the presence of chalcopyrite, the more likely iron oxide is produced on the surface, and the iron oxide causes a decrease in properties. However, as is clear from FIG. 4, when cupric oxide is used which is heated under reduced pressure and replaced with nitrogen gas when returning to atmospheric pressure, these properties are hardly deteriorated.

(Example 2) Cupric oxide was heated to 200°C under reduced pressure of 6mmHg or less.
The results of measuring the amount of oxygen contained in each cupric oxide after heating it for 5 hours at -450°C, passing nitrogen gas through it, and returning it to atmospheric pressure. 46
Figure 6 shows the results of heating cupric oxide in a range of 0°C for 5 hours and then measuring the amount of oxygen contained in cupric oxide. The oxygen content of 100% here refers to the state in which the cupric oxide in the sample is considered to have completely become CuO, that is,
This state is based on the assumption that 1 s, 999 g of oxygen is contained for 63.546 g of copper. Therefore, the amount of oxygen is 100
% or less, it is considered that some cupric oxide exists in the form of cuprous oxide or copper, and when the oxygen content is ``j#1oo%'' or more, it is considered that adsorbed oxygen is included.

As is clear from Figure 5, the heating temperature is 80 to 350°.
In the C range, the amount of oxygen is constant and approximately 99.5% is considered to exist in the form of cupric oxide. On the other hand, 2
At 0″C, it has about 2% adsorbed oxygen, and 350
It is observed that the amount of oxygen rapidly decreases from 40oC to 40oC, and decomposition of cupric oxide begins to occur. Also,
When heated in a nitrogen stream, the change is slightly more gradual than when heated under reduced pressure, but it can be said that there is almost no difference.

Next, prototype batteries were fabricated using a mixture of cupric oxide and chalcopiphyte, which had been heat treated in a nitrogen stream at each of the above temperatures, as a positive electrode active material.

The positive electrode is made of cupric oxide, chalcopyrite, acetylene black as a conductive material, and a copolymer of ethylene tetrafluoride and propylene 67 fluoride as binders at a weight ratio of SO: 4.
The mixture was mixed at a ratio of o:s:s and molded under pressure. That is, the composition is exactly the same as that of the positive electrode of battery E (K') of Example 1. The battery is the one shown in FIG. 1, and the other configurations are exactly the same as in Example 1.

Table 2 shows a comparison of the heat treatment temperatures of cupric oxide and batteries using the same.

Table 2 The characteristics of these batteries (-M) when discharged immediately after manufacture under a load of 30 Ω at 20°C are shown in Figure 6.
After storage for 6 months at 0°C and 90% humidity, 20°C
Figure 7 shows the characteristics when discharged under a load of 30Ω.

As can be seen from FIG. 6, the battery 0°H with a large amount of oxygen exhibits a slightly higher voltage at the beginning of discharge, but the discharge time (discharge capacity) is the same as that of the battery jJJ. On the other hand, battery 1jL has a slightly lower discharge voltage and a slightly shorter discharge time. Because this is heat treated at high humidity of 400-450°C, the cupric oxide partially decomposes.
It is thought to be cuprous oxide. This result also suggests that thermal decomposition of cupric oxide begins at a temperature exceeding about 360'Q.

Looking at the storage results of the batteries under high temperature and high humidity conditions in FIG. 7, it is seen that the characteristics of batteries G and H are clearly deteriorated.

This is similar to the result when the cupric oxide of Example 1 was not heat treated, and from this it can be seen that the heat treatment temperature needs to be at least 80°C or higher.

The same battery test as in Example 2 was also conducted when cupric oxide was heat treated under reduced pressure of 6 mHg or less and replaced with nitrogen gas, but the results were exactly the same.

However, even when similar tests were performed by replacing nitrogen gas with inert gases such as argon gas or helium gas, the results were exactly the same.

Furthermore, the chalcopyrite used in Examples 1 and 2 was synthesized from cuprous sulfide and iron disulfide (CuFeS).
x, x = 1. s2), but depending on the synthesis conditions, different values of X (1.8 to 2.0 in X) may be used, and natural chalcopyrite (GuFeS
Similar results were obtained using xgin2).

Effects of the invention As described above, the present invention has been achieved in an organic electrolyte battery using a positive electrode having cupric oxide as the main active material and chalcopyrite as the opening material, and a negative electrode having lithium or an alloy mainly composed of lithium as the active material. According to the invention) cupric oxide is heat treated in a nitrogen gas or inert gas atmosphere or under reduced pressure, preferably in a temperature range of 80 to 360'C, followed by nitrogen gas or inert gas blowing. By performing the treatment to return the battery to normal pressure, good characteristics can be obtained when storing the battery under high temperature and high humidity conditions, and its industrial value is extremely large.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the button-shaped organic electrolyte battery used in Example 1 and Example 2, and Figure 2 is a cross-sectional view of the button-shaped organic electrolyte battery used in Examples 1 and 2. Figure 3 is a diagram showing the battery characteristics after storage when untreated cupric oxide is used, and Figure 4 is a diagram showing the battery characteristics after storage when using untreated cupric oxide. A diagram showing the characteristics of a battery after storage when cupric oxide is used. Figure 6 is a diagram showing the temperature during heat treatment and the amount of oxygen in cupric oxide. Figure 6 is a diagram showing the characteristics of a battery when heated at various temperatures. FIG. 7 is a diagram showing the discharge characteristics of a battery when treated cupric oxide is used, and FIG. 7 is a diagram showing the discharge characteristics of the battery after the batteries are stored under high temperature and high humidity. 2... Lithium negative electrode, 3... Separator, 4... Positive electrode, 5... Case. Name of agent: Patent attorney Toshio Nakao and one other name
1 figure
31.2t) Figure 6 'tnx (x>

Claims (3)

[Claims] (1) Main active material obtained by heating cupric oxide (CuO) in a nitrogen gas or inert gas atmosphere or under reduced pressure, and replacing it with the above gas when returning to atmospheric pressure, and chalcopyrite. A method for producing an organic electrolyte battery comprising a positive electrode made of a mixture of lithium and a sub-active material, and a negative electrode made of lithium or a lithium-based alloy. (2) The method for producing an organic electrolyte battery according to claim 1, wherein the heat treatment temperature of cupric oxide is 80° to 350°C. (3) The proportion of cupric oxide in the positive electrode active material is 8 by weight.
The method for producing an organic electrolyte battery according to claim 1 or 2, wherein the content is 0 to 60%.