JPS5986155A - Manufacture of positive active substance for organic electrolyte battery - Google Patents

Abstract

PURPOSE:To obtain carbon fluoride which shows good storing characteristic and flat discharge characteristic from the initial discharge by irradiating carbon fluoride with ultraviolet ray in the alkali alcohol solution in order to partly obtain fluorine. CONSTITUTION:Carbon fluoride is irradiated with the ultraviolet ray in the alkali alcohol solution in order to partly obtain fluorine. For example, carbon fluoride with content of fluorine of 62.5wt% and particle size of 45mu or less obtained from the raw material of petroleum coke is penetrated and suspended by a processing solution obtained by solving sodium hydrate of 1-equivalent into methanol ata the rate of 100g/l and is then irradiated with the ultraviolet ray for 1-5hr using a mercury lamp. After the washing and drying, the carbon fluoride is attached with acethylene black as the conductor material and stylenebutadiene rubber bonding material. The positive black mix pellet 5 thus obtained is used for configurating a flat type lithium battery.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a so-called organic electrolyte battery that uses a light metal such as lithium, sodium, magnesium, or aluminum as a negative electrode active material and an organic electrolyte. More specifically, the present invention relates to a method for producing fluorocarbon, which is the positive electrode active material of this battery.

Structure of conventional example and its problems Fluorinated carbon has a large theoretical discharge capacity density of 864 mAH/g and is chemically stable, so it has good storage properties in organic electrolytes. Because it has very good voltage flatness during discharge, it is widely used as a positive electrode active material for lithium batteries.

However, the voltage at the beginning of the discharge is slightly lower than the flat voltage at the middle of the discharge, and a so-called voltage rise phenomenon is observed (a in FIG. 2). The main use of lithium batteries is
For example, there are power supplies for small electronic devices such as calculators and electronic watches. In order to maintain and improve the reliability of these electronic devices, battery voltage fluctuations are required to be as small as possible, and the phenomenon of voltage rise at the beginning of discharge of fluorocarbon/lithium batteries is minimized to ensure more stable discharge. It is hoped that the characteristics will be obtained.

Conventionally, in order to improve this property, the addition of surfactants,
Additions such as manganese dioxide, which has a higher initial voltage than fluorocarbon, have been proposed, but if other substances enter the battery system, side reactions may occur, and stability with the electrolyte may deteriorate over a long period of time. There is a problem with storage stability.

On the other hand, as an example of treating fluorocarbon in alcohol,
It is known to treat with alkali/acid or potassium iodide to improve storage stability. However, these reactions alone can remove weak C...F bonds called free fluorine contained in fluorocarbons, but they also cleave C-F bonds, which are co-Ij bonds. It did not reach the point of
This was insufficient for significant improvement in the early stage of t1.

Purpose of the Invention The present invention aims to improve such a voltage rise phenomenon at the initial stage of discharge by modifying fluorocarbon, which has good storage stability and exhibits excellent discharge characteristics from the early stage of discharge. The purpose is to provide fluorocarbon as a positive electrode active material.

Constituent structure of the invention Fluorocarbon has a layered structure consisting of C-C, C-F bonds, but '::cp2゜-CF3 groups are present at the ends of the layer plane, and the fluorine content in the fluorocarbon is Theoretical value 61.3
If it is larger than % by weight (F/C=1.0), it is thought that this is due to the presence of these fluorines. The fully fluorinated fluorocarbon particle surface has this "::
ay2. It is thought that it is thinly covered with a layer of -CF3 groups. Therefore, fluorocarbon is a substance with a lower surface energy than polytetrafluoroethylene (PTFE), and has physical properties that make it difficult to wet with organic solvents.

Furthermore, the discharge reaction mechanism with lithium is thought to be a mechanism in which Li+ invades between the layers of fluorocarbon, but at the beginning of discharge, the fluorocarbon particle surface, that is, CF2. -C
It is thought that the F3 group is largely involved.

The present invention involves defluorination of the surface of fluorinated carbon particles, that is, -CF2. -CF3
This method is characterized by the discovery that the characteristics at the initial stage of discharge can be improved by reducing the group.

DESCRIPTION OF EXAMPLES The fluorinated carbon was made from petroleum coke and had a fluorine content of 62.6% by weight and a particle size of 46 μm or less. A treatment solution is prepared by dissolving 1N of sodium hydroxide in methanol or ethanol, and fluorocarbon is wetted and suspended in this solution at a ratio of 100J; UV rays were irradiated for a certain period of time.

The following table shows each treatment condition and the changes in fluorine content and hue after treatment. Note that each treatment was performed at room temperature.

The fluorinated carbon subjected to each treatment was thoroughly washed with water and dried, and then a flat battery shown in FIG. 1 was fabricated as a prototype, and its characteristics were evaluated.

In the figure, 1 is a sealing plate, 2 is a lithium negative electrode, 3 is a separator made of polypropylene nonwoven fabric, 4 is a resin gasket, and 5 is 100 parts by weight of fluorocarbon subjected to each treatment and 10 parts by weight of acetylene black as a conductive material. Made of 6 parts by weight of styrene-butadiene rubber adhesive, diameter 14mm, thickness 0.60+
n+n positive electrode mixture pellets, 6 a positive electrode current collector, and 7 a case. The electrolytic solution used was one in which lithium borofluoride was dissolved at a concentration of 1 mol/l in a mixed solvent of propylene carbonate and dimethoxyethane at a volume ratio of 1:1.

The battery characteristics were evaluated by a constant resistance continuous discharge test at 13 ohms at 20'C. Fig. 2 shows the discharge characteristics of the battery immediately after assembly, and Fig. 3 shows the relationship between the discharge capacity and the fluorine content when the final voltage was set to 2.4 V under the above-mentioned discharge conditions. Furthermore, after storing this battery at 60° C. for 3 months, it was discharged under the same conditions as above, and the results are shown in FIG.

As shown in Figure 2, 'l!' in the early stage of discharge. 11'l &
In the case of J alkali treatment G), there is no difference from untreated (a), but in the case of ultraviolet treatment, there is a noticeable change in J'J ;~
It can be seen that it is J-+. However, the voltage at the initial stage of discharge is
The greater the degree of reduction, i.e. the lower the fluorine content, the more
Although the voltage is high, the fluorine content is greatly reduced (d, e
), a clear decrease in capacity can be seen.

From FIG. 3, which shows the relationship between the fluorine content and the discharge capacity, it can be seen that a discharge capacity equal to or higher than that of the untreated (a) can be obtained when the fluorine content is 59 g@φ or more. As can be seen in Figure 3, the discharge capacity does not change in proportion to the fluorine content, and it is thought that the ultraviolet irradiation treatment of the present invention will improve the discharge utilization rate. No. Therefore, it is thought that a different trend from that shown in Fig. 3 can be seen for guests with low load discharge, which has a better utilization rate: i4: li. However, even if it is assumed that the fluorine content is proportional to the fluorine content, a product with a fluorine content of about 69 cm will only reduce the capacity by about 6%. There is no significant difference from the discharge capacity required for voltage stabilization, and there is almost no decrease in capacity during actual use.

Further, FIG. 4 shows the discharge characteristics of fluorocarbons subjected to ultraviolet irradiation treatment and alkali treatment after high temperature storage.

In both untreated (a) and treated example (b-CI), the discharge starting voltage is lower than the discharge immediately after assembly, but this decrease in starting voltage is different from untreated a and treated example b-q. It is the same or smaller, and the negative electrode lithium side is also considered to be a factor, so it is thought that the storage stability of fluorocarbon treated with each treatment is equal to or better than untreated at the early stage of discharge. Further, it can be seen that the voltage difference between the flat part in the early stage of discharge and the flat part in the middle stage of discharge is more pronounced in case a than in the discharge immediately after assembly, but it is very small in cases b to f where ultraviolet rays were irradiated. In addition, the decrease in discharge capacity due to storage is e
However, in other processing example b-
d, f, and q are at the same level. Therefore, it can be seen that the storage stability of fluorocarbon treated with ultraviolet rays is equivalent to that of untreated carbon when the fluorine content is up to about 59% by weight (b, c, f).

Effects of the Invention According to the present invention, as shown in Figures 2 to 4, the voltage characteristics at the initial stage of discharge are improved by irradiating ultraviolet rays in an alkaline alcohol solution and using fluorocarbon whose surface has been slightly reduced. Therefore, it is possible to provide a battery that has good voltage flatness from the initial stage of discharge and also has good storage stability.

This effect is caused by reduction of the surface of fluorocarbon particles by ultraviolet irradiation, that is, CF2. This is thought to be due to the fact that by removing the -CF3 group, the wettability with respect to the organic electrolyte was good, and lithium was easily diffused between the layers. It is believed that the alkali has the function of promoting the defluorination reaction from 10F2 and the like caused by the above-mentioned ultraviolet rays.

In addition, the wet heat of fluorocarbon relative to n-butanol after irradiation treatment increases by 10 to 60%, and the diffusion coefficient of Li+ between fluorocarbon layers at the beginning of discharge increases several times to several tens of times. This seems to support the above hypothesis. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a flat battery in an embodiment of the present invention;
FIG. 2 is a diagram showing the discharge characteristics of the battery of the present invention immediately after assembly, and FIG. 3 is a diagram showing the relationship between fluorine content and discharge capacity.
FIG. 4 is a diagram showing the discharge characteristics after storage at 60° C. for 3 months. 1・°“°・Sealing plate, 2... Negative electrode, 3...
・・・Senokurator, 6・・・Positive electrode, 7・・・・・・
·Case.

Claims (2)

[Claims] (1) An organic electrode #li! characterized by partially defluorinating fluorinated carbon by subjecting it to ultraviolet irradiation treatment in an alkaline alcohol solution. (Production method of positive electrode active material for batteries. (2) A patent in which the fluorine content after defluorination treatment of fluorocarbon is 59% by weight or more +f! 'j seeking rlij
'jCathode active material for organic electrolyte batteries described in item 1 1jj■
The manufacturing method.