JPS585967A - Battery - Google Patents

Abstract

PURPOSE:To improve the discharge characteristic of a carbon-fluoride light-metal system battery by obtaining carbon fluoride having a large activity from carbon black having a specific surface area of above several hundreds m<2>/g, and adding an appropriate amount of thus prepared carbon fluoride to carbon fluoride made from petroleum coke or the like. CONSTITUTION:A battery includes a negative electrode made of a light metal used as an active material, a positive electrode made of carbon fluoride used as an active material, and an organic electrolyte. The above positive active material is prepared by adding carbon fluoride, which is obtained by fluorinating carbon black having a specific surface area of above 800m<2>/g, to carbon fluoride o btained by fluorinating natural graphite, artificial graphite or petroleum coke. Here, a remarkably good result can be obtained by using carbon black with a grain diameter of below 1mu. Besides, in order to achieve such a good result without deteriorating the energy density of the battery, the content of carbon fluoride obtained from carbon black should be 5-20% by weight of the amount of the active material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses light metals such as lithium, magnesium, and aluminum, or alloys mainly composed of them, as a negative electrode active material, fluorocarbon as a positive electrode active material, and propylene carbonate and γ-butyrolactone as an electrolyte. , 1-2 dimethoxyethane, 1-3 dioxolane, tetrahydrofuran, etc., alone or in a mixture, with an inorganic salt such as lithium perchloride, lithium fluoroborate, or aluminum chloride dissolved in a so-called fluorocarbon/light metal system. This relates to improvements in batteries.

Conventionally, positive electrode active materials for organic electrolyte lithium batteries include carbon fluoride, manganese dioxide, silver chromate, copper oxide,
Various attempts have been made to use solid active materials such as copper fluoride, nickel chloride, and bismuth oxide, liquid active materials such as thionyl chloride and sulfuryl chloride, and gaseous active materials such as sulfur dioxide.

However, it can be said that the fluorocarbon active material is the most excellent from a comprehensive viewpoint such as the energy density of the active material, stability with respect to electrolyte, ease of handling, and safety.

Fluorocarbon is an inorganic polymer obtained by directly reacting fluoride and carbon at high temperatures, and has the general formula (C
F, )n (r-=1), and even if amorphous carbon is used as a raw material, it will be highly crystalline like that obtained from graphite, so it is distinguished from fluorocarbons such as CF4, and fluorocarbons It is called.

Although this fluorinated carbon is completely stable chemically, it is very active electrochemically, so it exhibits excellent properties when used as an active material in batteries.

In particular, when petroleum coke, natural graphite, two-synthetic graphite, etc. are used as the raw material carbon, unlike other carbon materials, the yield of fluorocarbon generation is high, and when used as a battery active material, the discharge utilization rate increases quickly. Although it has characteristics such as excellent flat voltage characteristics, it also tends to have a slight delay in the voltage rise in some parts at the initial stage of discharge.

Recently, lithium batteries have attracted attention as a power source for electronic watches due to their excellent leakage resistance and low self-discharge, but there is a risk that the initial voltage ramp-up may be a problem, so improvements are needed. No.

In the present invention, the fluorocarbon produced by using a carbon blank with a specific surface area of several hundred ba/y or more, particularly 800 gp as a carbon raw material, has a high degree of activity, and when this is used as an active material, It was discovered that while it has the characteristic of high initial discharge voltage, it also has the drawbacks of poor voltage flatness and discharge utilization. The purpose of this is to improve battery characteristics.

In addition, in fluorocarbon lithium batteries, the fluorocarbon that is the IF electrode active material is either an insulator itself or generates conductive carbon as the discharge reaction progresses, so the electrical conductivity of the electrode increases. It contributes to the discharge characteristics of our batteries. Therefore, the discharge characteristics of the battery, particularly the discharge voltage, vary slightly depending on the state of carbon, which is a discharge product.

That is, the finer the generated carbon particles, the more they contribute to the conductivity of the electrode, and the higher the flat voltage during discharge becomes.

In general, fluorocarbon positive electrodes produce amorphous carbon that is finer than the raw material carbon through discharge, but of course, the finer the raw material carbon, the finer the carbon produced by discharge, which improves the voltage characteristics. Can be done.

Therefore, the smaller the raw carbon particles are, the better the discharge characteristics will be. Furthermore, it has been found that the effect is particularly remarkable when a carbon blank with a particle size of 1 μm or less is used.

At the same time, as long as these effects are achieved and the energy density of the battery is not impaired, the amount of fluorocarbon added, which is made from carbon black, should be 5 to 20% by weight based on the total active material. Ta.

In general, activated carbon is an example of carbon having a large specific surface area, and its specific surface area is about 1000 to 3000 WVy, and its particle size is several microns or more. When fluorinated fluorocarbon using this is added to the fluorocarbon made from petroleum coke, etc., the initial voltage rise characteristics are obviously improved fr.

However, since the particle size was as large as several microns, almost no change was observed in the flat voltage characteristics.

On the other hand, carbon black has a smaller particle size than activated carbon and a smaller surface area of several +rrt/y.

However, a special kind of furnace black, such as E, C, Black manufactured by Akzo Corporation in the United States, is an amorphous granular powder with a specific surface area of 1000g/y9.
The particle size is several tens of microns, and the particles are fluorinated to form fluorocarbon, which is in the range of 6 to 2% by weight of the total amount of active material.
Depending on the degree of addition, not only the initial voltage rise characteristics were improved, but also the flat voltage characteristics could be improved at the same time.

The effects will be explained below using examples.

FIG. 1 shows a fluorocarbon/lithium flat battery. In the figure, 1 is a case made of a stainless steel plate with a thickness of 0.26 m, and 2 is a sealing plate made of the same material.

Reference numeral 3 denotes a nickel lath plate with a thickness of o and i m welded to the inner surface of the sealing plate 2, and a negative electrode 4 is constructed by pressing a lithium lath plate with a thickness of 0.24 m and a diameter of 18 mm onto this plate. There is. 5
is a carbon heptonide positive electrode with a diameter of 17M and a thickness of 0.581 ul. Reference numeral 6 is a tele/plate positive electrode current collector, 7 is a polypropylene liquid retaining material, 8 is a polypropylene separator, and 9 is a polypropylene gasket.

The electrolytic solution used was one in which 1 mol/e of lithium borofluoride was dissolved in a solvent in which globylene carbonate and 1-2 dimethyneethane were mixed at a volume ratio of 1:1.

After injecting 0.18 CG of this electrolyte solution, the battery was sealed, and the size of the battery was set to 23 B in diameter and 2 m in height.

Studies were conducted using various positive electrodes in the configuration described in -1-.

The positive electrode used was a mixture of 100 parts by weight of carbon heptanoide active material, 10 parts by weight of acetylene black as a conductive agent, and 5 parts by weight of styrene-butadiene rubber as a binder 11, and the mixture was molded under pressure.

As the +-E electrode active material, battery A uses fluorinated carbon by fluorinating petroleum coke, with a specific surface area of 2000 d/p.
Battery B uses fluorinated carbon, which is made by fluorinating activated carbon with a particle size of several microns to several tens of microns, and battery B uses fluorinated carbon, which uses fluorinated amorphous carbon black with a specific surface area of 1000g/y2 and a particle size of several tens of microns. The battery used was designated as battery C.

Since the thickness of the positive electrode after molding was constant in both cases, the positive electrode using fluorocarbon of petroleum coke with good moldability had the highest packing density, and the positive electrode weight was 0.2y for battery A (theoretical filling amount 150 mAh ), battery B is 0.191 (theoretical filling capacity 142 mAh), battery C is 0.18 y (
The theoretical filling amount was 135 mAh).

Figure 2 shows the characteristics of these batteries when they were discharged at a temperature of 20 DEG C. and a constant resistance of 13 Ω as a load.

Battery A has both voltage stability and discharge amount of electricity, but
A slight voltage delay is observed at the beginning of discharge. On the other hand, batteries B and C have no initial voltage delay and exhibit high voltage characteristics, but are inferior to battery A in terms of voltage uniformity and discharged electricity amount.

This high voltage characteristic at the initial stage of discharge is clearly due to the large specific surface area of the original H family carbon.

That is, an amorphous carbon blank with a particle size of several tens of micrometers as shown in 11 is produced by an appropriate manufacturing method, and its specific surface area becomes 6oowt/
y, 7oont/y, soogo/P.

1000n? /7. Make it 2000 go/y, -
Batteries manufactured under the same conditions as battery C described above are called batteries C4, C2, C3, and C1C4, respectively, and the temperature is 2°C.
, 13kQ constant resistance load is shown in the third figure.

As is clear from Fig. 3, the discharge voltage characteristics are proportional to the specific surface area of the raw material carbon black, and the branching point of the voltage delay at the beginning of discharge occurs when the specific surface area is 800 rrt /
y, and it can be seen that if a raw material carbon blank having a specific surface area smaller than this is used, no voltage rise delay occurs at the initial stage of discharge.

Next, as a positive electrode active material, a battery A with only fluorocarbon of petroleum coke and a battery with 10Ji amount percent added to the fluoride carbon of petroleum coke of A and the fluoride carbon of activated carbon were used.
Similarly, a battery E, 10 in which fluorinated carbon of the amorphous carbon blank of the active material of Battery C was added with a pentad needle percentage was used.
A battery with 0 weight percent addition is designated as F, and a battery with 20 weight percent addition is designated as G. The weight of the positive electrode is 02y (theoretical filling amount: 15
0 mAh), battery E is 0.2y (theoretical filling capacity 150
mAh), battery F is 0.196y (theoretical filling amount 1.
46 mAh), battery G was 0.19 y (theoretical charging capacity 142 mAh).

r.

Figure 4 shows the early discharge of batteries A, D and E oils at a constant resistance of 20'C (20'C).

As can be seen from Figure 4, by adding an appropriate amount of fluorocarbon produced from raw material carbon blank with a large specific surface area to fluorocarbon produced from petroleum coke, which has excellent voltage flatness and discharge utilization efficiency, these The voltage \'A rise characteristic at the initial stage of discharge can be improved without impairing the characteristics.

Furthermore, as shown in Figure 2, the discharge voltage characteristics of carbon heptide, which is made from activated carbon as a raw material, fluorocarbon, and amorphous carbon blank, have almost no change in discharge voltage characteristics. When added to carbon 7 fluoride prepared in April, battery F had a flatter discharge, even though the amount added was the same for battery F and battery F (10%), as is clear from Figure 4. Voltage is high. This is also recognized from batteries B and C in FIG. 2, and is thought to be related to the particle size of the raw material carbon.

Therefore, by changing the particle size of amorphous carbon black,
A battery is manufactured by producing fluorinated carbon and adding it to fluorinated carbon made from petroleum coke under the same conditions as Battery F.
The relationship between the flat voltage value when discharged at a temperature of 20°C and a constant resistance load of 13 Ω and the particle size of carbon black, the raw material for carbon hepta-node of the added amorphous carbon blank, is shown in Figure 5.
As shown in the figure.

As is clear from Fig. 5, the flat voltage (-, 1, 2, and 76 V is constant at -, 1, 2, and 76 V when the particle size is less than 1 μm, but it decreases when the particle size becomes JZ'', and when the particle size exceeds 10 μm, the voltage increases again at 2 V). .7V
becomes constant. Therefore, it can be seen that in order to obtain good flat voltage characteristics, it is desirable that the grain size be less than III.

It was confirmed that the same effect was shown not only for fluorocarbon produced from 1 petroleum coke, but also for fluorocarbon produced from natural graphite and 1 artificial graphite.

As described above, it can be said that the present invention is of great value in improving the characteristics of batteries using fluorinated carbon as a positive electrode active material.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a fluorocarbon/lithium flat battery according to an embodiment of the present invention, Figure 2 is a discharge characteristic diagram of batteries using different fluoride carbon as the positive electrode active material, and Figure 3 is an amorphous battery. Figure 4 shows the discharge characteristics of batteries using fluorocarbons with different specific surface areas of carbon black, and Figure 5 shows the discharge characteristics of batteries using two types of fluorocarbons. FIG. 3 is a diagram showing the relationship between the force to change and the particle size of bomb black and the flat voltage. 1..@110 cases, 2..■ Punching board, 4..
- Negative electrode, 6... Sorated carbon positive electrode, 7...
・Liquid retention, 8------...Separator 9 @1111
...9 gaskets. Name of agent: Patent attorney Toshio Nakao and one other person (InIA)

Claims (3)

[Claims] (1) Consisting of a negative electrode using a light Kanai Chi active material, a positive electrode using fluorocarbon as an active material, and an organic electrolyte, where the positive electrode active material is natural graphite, artificial graphite, or petroleum carbon added. A battery characterized by: (2) The battery according to claim 1, wherein the carbon blank as a raw material for the fluorinated carbon added to the positive electrode has a particle size of 1 μm or less. (3) The battery according to claim 1 or 2, wherein the fluorinated carbon added to the positive electrode is 5 to 20 weight percent of the total active material.