JPS63124369A - Manufacture of organic electrolyte battery - Google Patents

Abstract

PURPOSE:To heighten the working voltage of a battery in the 40% or more deep discharge and to increase the effective discharge capacity by using bismuth trioxide heated at 650 deg.C or more as a positive active material. CONSTITUTION:A positive active material is prepared by heating bismuth trioxide having a purity of 99.99% in the atmosphere at 300-1000 deg.C for 5 hours, and crushing it in particles having a particle size of 100mum or less. As the comparison, bismuth trioxide powder is used without heat treatment. The bismuth trioxide, carbon conductor, and a fluorine resin binder are mixed in a ratio of 94.5:5:0.5. The mixture is molded in a pellet together with a positive ring made of stainless steel having L-shaped cross section and dried under a reduced pressure at 100 deg.C for 10 hours to form a positive electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the improvement of an organic electrolyte battery that uses lithium as the main active material for the negative electrode and bismuth trioxide Bi2O3 as the main active material for the positive electrode.

In organic electrolyte batteries that use lithium as the negative electrode active material, batteries with various operating voltages are possible depending on the type of active material used for the positive electrode, but in practical terms, the 3-inch type, which has an operating voltage of approximately 3. 1, which has an operating voltage of approximately 1.5
, 5V type.

Known positive electrode active materials belonging to the 1.5V type include cupric oxide, iron sulfide, iron disulfide, lead oxide, bismuth trioxide, and the like. Among these, batteries using bismuth trioxide have a high operating voltage of 1.5V to 1.8V, so they are a particularly advantageous battery system for applications requiring large current discharge. The present invention relates to an improvement in the positive electrode of a lithium-organic electrolyte battery using such bismuth trioxide as the positive electrode.

[Conventional technology]

Conventionally, in this type of battery, for example, when manufacturing a button-type battery, a positive electrode has been made as follows. That is, the active material bismuth trioxide, an electric agent such as carbon powder or metal powder such as graphite or carbon black, and a resin binder such as fluorine resin or polystyrene are mixed in a predetermined composition ratio, and then this positive electrode is mixed. A predetermined amount of the mixture is filled into a mold of a molding machine and pressure-molded to form a pellet-like positive electrode molded body. The positive electrode pellets thus obtained are heated at a temperature within a range where thermal decomposition of the resin binder and oxidation of the conductive agent do not occur.
After being sufficiently dehydrated by heating and drying under reduced pressure at a temperature of 300° C. or less, it is assembled into a battery. An organic electrolyte using bismuth trioxide as a positive electrode active material is disclosed in, for example, JP-A-52-124.
It is disclosed in Japanese Patent Publication No. 25 and Japanese Patent Publication No. 59-49673.

[Problem that the invention seeks to solve]

However, when a battery made using bismuth trioxide as the positive electrode active material is discharged using the conventional method described above, the discharge characteristics show two stages of discharge voltage, as shown in a in Figure 2. , the operating voltage becomes low when the depth of discharge is about 40% or more. For this reason,
When this battery is used in equipment that requires large current discharge,
Due to a drop in battery voltage, even if there is still sufficient battery capacity remaining, the voltage required to operate the device normally cannot be obtained, resulting in a significant decrease in effective battery capacity (life). Ta.

The present invention achieves this by improving the bismuth trioxide positive electrode.
The purpose of this invention is to increase the operating voltage of this type of battery, particularly at a depth of discharge of about 40% or more, and to improve the effective discharge capacity.

[Means for solving problems]

As a result of various studies to solve the above-mentioned problems, the present inventors have found that by using bismuth trioxide heat-treated at a temperature of 650°C or higher as the positive electrode active material, the operating voltage of this type of battery can be increased. It has been found that the operating voltage is particularly improved at a depth of discharge of about 40% or more, and the effective discharge capacity is significantly improved.

That is, when manufacturing a positive electrode, before mixing bismuth trioxide with a conductive agent, a binder, etc., 65% of bismuth trioxide is added.
The material was heat-treated at a temperature of 0° C. or higher, and then mixed with a conductive agent and a binder if necessary, and molded into a predetermined shape. The atmosphere for the heat treatment may be any atmosphere that does not reduce bismuth trioxide, such as air, inert gas, or vacuum.

In addition, when powdered bismuth trioxide is heat-treated at a temperature of 650°C or higher, it hardens into a bond when cooled due to sintering, melting, etc., so in order to uniformly mix it with the conductive agent and binder, It is preferable to thoroughly grind the materials into fine particles of 100 μm or less before mixing.

In particular, when heat-treated at a temperature higher than the melting point of bismuth trioxide of 820° C., it melts and becomes a strong bond after cooling, so it is important to sufficiently crush it into fine particles.

[Effect]

As mentioned above, when a battery made using bismuth trioxide heat-treated at a temperature of 650°C or more is discharged, the operating voltage, especially at a depth of discharge of about 40% or more, becomes high.
As a result, the effective discharge capacity up to a certain cut-off voltage is significantly improved.

The reason why the operating voltage is improved is not necessarily clear, but it is presumed as follows. That is, 650 bismuth trioxide
When heat treated at temperatures above 0.degree. C., the atoms constituting each particle of bismuth trioxide move significantly, causing subtle changes in the crystal surface and internal structure of each particle, and increasing electrochemical activity.

On the other hand, at temperatures below 650° C., such atomic movement is small, so the operating voltage is not improved.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 The positive electrode active material was a bismuth trioxide powder with a purity of 99.99χ that was heat-treated in the air at a temperature of 300 to 1000°C for 5 hours, cooled, and then ground to a particle size of 100μ2 or less, and a comparison. As an example, a raw powder without heat treatment was used. This heat-treated or untreated bismuth trioxide, a carbon conductive agent (graphite or carbon black, etc.), and a binder made of a fluororesin are mixed in a weight ratio of 94:5.
: 5 : Mixed at a ratio of 0.5, SU with a cross-sectional shape
The positive electrode was formed by pressure molding into a pellet together with a positive electrode holding ring made of S, and then dried under reduced pressure at 100° C. for 10 hours. The positive electrode thus produced had a diameter of 9.0 m, a thickness of 1.1 fins, and a theoretical capacity of 90 mAH.

FIG. 3 is a sectional view of a battery showing an example of the present invention. In the figure, ■ is a negative electrode can that also serves as a negative electrode terminal, and has a thickness of 0.
It is made by drawing a 22mm Ni/SUS clad plate. The negative electrode 2 was made by punching out a lithium sheet with a thickness of 1.3 mm to a diameter of 6.4 fl and press-bonding it to the inner surface of the negative electrode can. 6 is Ni/with a thickness of 0.22++n
This is a positive electrode can made of a SUS clad plate, and also serves as a positive electrode terminal. The positive electrode 5 is filled in this positive electrode can,
A separator 4 made of a microporous polypropylene sheet is placed thereon. 3 is an impregnating material that holds the electrolyte between the positive electrode and the negative electrode, and is made of a nonwoven fabric whose main element is polypropylene. 7 is a gasket mainly made of polypropylene, which is interposed between the negative electrode can 1 and the positive electrode can 6 to maintain electrical insulation between the positive electrode and the negative electrode, and at the same time, the opening edge of the positive electrode can can be bent inward and caulked. The battery contents are sealed and sealed. The electrolyte is a mixture of propylene carbonate and 1,2-dimethoxyethane.
; 1 mol/7 of lithium perchloride in 1 mixed solvent! The molten one was used.

The size of the battery is 9.5 mm in outer diameter and 3.0 mm in total thickness.

FIG. 2 shows that the heat treatment temperature of bismuth trioxide mentioned above is (a
), no heat treatment, (bl, 500°C, fcl, 6
50℃, (d+, 800℃, fel, 10
3 shows the Ω constant resistance discharge characteristics of the above battery at 24°C in the case of 00°C. From this result, when the heat treatment temperature of bismuth trioxide is 650°C or higher, the discharge voltage is higher than when it is lower than that, and the discharge voltage is especially high in the voltage flat part in mid-summer when the depth of discharge is about 40% or more. , Moreover, the discharge time until the cut-off voltage of 1.2■ is longer,
It can be seen that the discharge characteristics and effective discharge capacity are significantly improved.

FIG. 1 shows the relationship between heat treatment temperature and discharge capacity of bismuth trioxide. As is clear from the figure, when the heat treatment temperature of bismuth trioxide is 650°C or higher, the temperature reaches about 800°C.
The discharge capacity increases rapidly, and the increase in capacity is saturated at 850° C. or higher, and even if the heat treatment temperature is increased further, the capacity hardly increases and becomes almost constant. The reason for this is that the melting point of bismuth trioxide is 820°C, and bismuth trioxide is in a stable molten state at temperatures higher than this, so even if it is heat-treated at a temperature higher than this, the state after cooling is almost the same. It is presumed that this is because the In any case, it is clear from the figure that when bisnus trioxide is heat-treated at a temperature of 650°C or higher, the discharge capacity is improved compared to when it is heat-treated at a temperature lower than that or when it is not heat-treated. . In addition, the effect of heat treatment becomes particularly large at temperatures above 700°C, but at temperatures above 850°C, there is little further increase in capacity, and equipment such as electric furnaces for heat-treating bismuth trioxide, operating costs, and handling. Taking into consideration the shading, etc., the heat treatment temperature is preferably 700°C to 1000'C.

Example 2 In this example, a similar battery was made in the same manner as in Example 1, except that bismuth trioxide was heat-treated in nitrogen gas. Such a battery was heated at 24°C as in Example 1.
The results of Ω constant resistance discharge in step 3 were almost the same as in Example 1.

Example 3 In this example, heat treatment of bismuth trioxide was performed at 10-2 to 10
A similar battery was produced in the same manner as in Example 1, except that the test was carried out under a reduced pressure of -'T or r.

When such a battery was discharged at a constant resistance of 3Ω at 24° C. in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

Note that the organic electrolyte is γ-butyrolactone, propylene carbonate, and butylene carbonate.

1.2-dimethoxyethane, latrahydrofuran.

L as a supporting salt in an aprotic organic solvent such as dioxolane or dimethylformamide alone or in a mixed solvent.
iC7! O,, Li BFa, Li PF4゜LiD
An organic electrolyte in which an ionically dissociable salt such as FaS03 is dissolved may be selected.

〔Effect of the invention〕

As detailed above, the present invention uses bismuth trioxide heat-treated at a temperature of 650°C or higher as a positive electrode active material, thereby increasing the operating voltage of Li/Biz Oy-based batteries, particularly the depth of discharge of about 40%. It has excellent effects such as increasing the operating voltage, significantly increasing the effective discharge capacity, and significantly improving the discharge characteristics.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between heat treatment temperature and discharge capacity of bismuth trioxide, Figure 2 is a comparison diagram of discharge characteristics of batteries using bismuth trioxide heat treated at various temperatures, and Figure 3 is a diagram showing the relationship between heat treatment temperature and discharge capacity of bismuth trioxide. FIG. 2 is a cross-sectional view showing an example of a battery that was used. ■...Negative electrode can 2...Negative electrode lithium 3...Impregnating material 4...Separator 5...Positive electrode 6
...Positive electrode can 7...Gasket 8...Positive electrode holding ring or higher

Claims (2)

[Claims] (1) Consisting of at least a negative electrode containing lithium as the main active material, an organic electrolyte, and a positive electrode, and 650% as the positive electrode active material.
Bismuth trioxide Bi_2O_ heat treated at temperatures above ℃
3. A method for manufacturing an organic electrolyte battery, characterized by using the method. (2) In the atmosphere, inert gas, or vacuum 7
Bismuth trioxide B heat treated at a temperature of 00~1000℃
The method for manufacturing an organic electrolyte battery according to claim 1, characterized in that i_2O_3 is used as a positive electrode active material.