JPS618852A - Nonaqueous electrolyte cell - Google Patents

Abstract

PURPOSE:To make it possible to restrain the rapidly increasing of internal resistance of a cell accompanied with its discharging by using a positive electrode made of the material which increases its apparent volume by discharge reaction and a separator made of a micro-porous resin film and also by providing a formed electrolyte layer between the separator and an electrode. CONSTITUTION:A positive electrode 1, which is made of the mixture composed of active material of iron disulfide, conductive material of graphite and binding agent of fluororesin powder, is formed by firing after pressure forming the mixture, and a negative electrode 2 is made of lithium rolled plate of punched one. And, a separator 3, is made of micro-porous polypropylene film of punched one, and an electrolyte layer 4 composed of electrolytic solution is provided between the negative electrode 2 and the separator 3 so as to fill the void between them. Thereby, when the volume of the positive electrode becomes larger, the rapidly increasing of internal resistance does not occure because of its short distance between the positive electrode and the negative electrode. And, the solution retention performance of micro-porous polypropylene film is lower when compared with that of polypropylene unwoven fabric, however, any trouble may not be happened since the formed electrolyte layer made of only electrolytic solution is provided between the separator and the negative electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a non-aqueous electrolyte battery equipped with a positive electrode whose apparent volume increases due to a discharge reaction.

(Example) Prior art For example, fluorinated carbon, silver chromate, manganese dioxide, etc. disclosed in Japanese Patent Publication No. 54-35653, metal sulfides disclosed in Japanese Patent Application Publication No. 57-174871, Copper oxide, bismuth oxide, etc. have the property of increasing their apparent volume due to a discharge reaction, so when a non-aqueous electrolyte battery is incorporated with such materials as positive electrode active materials,
There are problems as described below.

That is, as described in the above-mentioned prior art document,
Polypropylene nonwoven fabric is generally used as a separator member in this type of battery, but when the volume of the positive electrode increases due to a discharge reaction, the separator made of polypropylene nonwoven fabric interposed between the positive and negative electrodes is compressed and the electrolyte impregnated and retained is squeezed. As a result, the polypropylene nonwoven fabric in which almost no electrolyte is present is partially located between the positive and negative electrodes, causing a rapid increase in internal resistance and deterioration of battery characteristics.

(c) Problems to be Solved by the Invention The present invention attempts to suppress the rapid increase in internal resistance accompanying discharge of a non-aqueous electrolyte battery equipped with a positive electrode whose volume apparently increases due to a discharge reaction. It is something to do.

(d) Means for Solving the Problems The present invention provides a negative electrode whose active material is a light metal such as lithium or sodium or an alloy thereof, a positive electrode whose volume apparently increases due to a discharge reaction, and one of the electrodes. A nonaqueous electrolyte battery includes a separator made of a microporous resin film disposed on a surface facing the other electrode, and an electrolyte layer formed between the other electrode and the separator.

(E) Function According to the battery of the present invention, when the apparent volume of the positive electrode increases due to a discharge reaction, this increase can be absorbed by the electrolytic solution layer, and the separator interposed between the positive and negative electrodes is extremely Because it is composed of a synthetic resin film, even if the volume of the positive electrode increases until the positive and negative electrodes come into contact with the separator where there is almost no electrolyte in some areas, the distance between the positive and negative electrodes is extremely short and the internal resistance is extremely low. It's not going to increase.

, (a): [1i(ffij FIG. 1 is a longitudinal cross-sectional view of a battery according to an embodiment of the present invention, (1)
is a positive electrode and contains 85% iron disulfide as an active material,
A mixture of 10% by weight of graphite as a conductive agent and 5% by weight of fluororesin powder as a binder was pressure-molded at a pressure of 2 tons/cm'' to a diameter of about 11.0 mm and a thickness of about 1.5 mm.
8mm pellets are fired at a temperature of 200-300"C. (2) is the negative electrode, about 2.2mm thick.
This is a lithium rolled plate with a diameter of approximately 7.5 mm. (3) is a separator with a thickness of about 0.025mm
Microporous polypropylene film with a diameter of approximately 11.0 mm
It consists of a punched out piece. (4) is an electrolytic solution layer made of an electrolytic solution that fills the gap between the negative a(2) and the separator (3).

The battery of FIG. 1 is assembled as follows.

That is, first, a lithium negative current collector (7) is fixed to the inner bottom surface of a negative electrode terminal/sealing lid (6) on which an insulating backing (5) is provided by insert molding on the periphery. (2) to prevent the lithium negative electrode (2) from falling even if it is reversed, and to create a gap between the lithium negative electrode (2) and the annular insulating backing (5) by t6°.
External can with one side also serving as positive terminal 8)
Press the positive ai (1) to the positive electrode current collector (9) that is fixed to the inner bottom surface of the case, place the separator (3) on the positive electrode (1), and in this state insert it into the opening of the outer can (8). The sealing lid (6
).

After placing the temporarily assembled battery in a sealed container and evacuating it, the battery was immersed in an electrolytic solution containing 1 mole of lithium borofluoride dissolved in a mixed solvent of propylene carbonate and 1.2 dimethoxyethane. The electrolyte is allowed to enter into the gap, and the gap is filled with the electrolyte to form an electrolyte layer (4).

After that, the opening edge of the outer can (8) is covered with an insulating backing (5).
to obtain a completed battery.

FIG. 2 shows a longitudinal cross-sectional view of a comparative battery, which differs from the battery of the present invention shown in FIG. 1 in that there is no electrolyte layer and that the separator members are different. Separator in comparison battery
13) is made of polypropylene nonwoven fabric with a thickness of about 0.5 mm.

FIG. 3 shows changes in voltage and internal resistance over time of battery A of the present invention and comparative battery B due to constant load discharge at 5 and 6 Ω at 20''C.

As is clear from Fig. 3, in the case of the cell A of the present invention, the internal resistance does not increase rapidly, so it shows a flat discharge voltage characteristic, whereas in the case of the comparative cell B, it shows a flat discharge voltage characteristic during the discharge. As a result, the internal resistance increases rapidly, resulting in a two-stage discharge voltage characteristic.

Considering the reason for this, in the case of Comparative Battery B, as discharge progresses, the electrolyte that had been retained in the polypropylene nonwoven fabric as a separator is squeezed out, and the polypropylene nonwoven fabric, in which almost no electrolyte is present, is partially disposed between the positive and negative electrodes. The thick polypropylene nonwoven fabric interposed therein acts as a kind of insulator, resulting in a rapid increase in internal resistance.

However, as the discharge progresses further, the thickness of the polypropylene nonwoven fabric decreases, so the internal resistance increase curve becomes gentler, but the battery voltage progresses at a lower value.

On the other hand, in the case of invention battery A, since a thin microporous resin film is used as a separator, even if the volume of the positive electrode increases, the distance between the positive and negative electrodes is short, so the internal resistance increases rapidly. There's nothing to do.

In addition, microporous polypropylene film has a lower liquid holding capacity by /J% than polypropylene nonwoven fabric, but in the battery of the present invention, an electrolyte layer containing only electrolyte is formed between the separator and the negative electrode, so there is no problem with this. There is no problem.

(G) Effects of the Invention As mentioned above, according to the battery of the present invention, even if a substance whose volume increases apparently due to a discharge reaction is used as the positive electrode, a microporous resin film is used as the separator, and the separator and electrode Since an electrolytic solution layer containing only an electrolytic solution is formed between the two, a rapid increase in internal resistance due to discharge is suppressed, and a flat discharge voltage characteristic is obtained, and its industrial value is extremely high.

In addition to the polypropylene film shown in the examples, a polyethylene film can also be used as the microporous resin film.

In addition, Japanese Patent Application Laid-Open No. 57-174871 exemplified as prior art
Although the publication also discloses forming an electrolyte layer between the separator and the negative electrode, the separator and t
′″″＋t yN ′) j o e b ＞″′″m
*tFfJbs-c°゛617During the charging process, the internal resistance increases rapidly as in the comparison battery.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a battery of the present invention, FIG. 2 is a longitudinal sectional view of a comparative battery, and FIG. 3 shows battery voltage characteristics and internal resistance characteristics with respect to discharge time. (1) Positive electrode, (2) Negative electrode, (3) Separator made of microporous resin film, (4) Electrolyte layer, (
5〉 Insulating backing, (6)... sealing lid, (8)...
・Exterior can.

Claims (1)

[Claims] (1) A negative electrode whose active material is a light metal such as lithium or sodium or an alloy thereof, a positive electrode whose apparent volume increases due to a discharge reaction, and micropores arranged on the surface of one of the electrodes facing the other electrode. A non-aqueous electrolyte battery comprising: a separator made of a synthetic resin film; and an electrolyte layer formed between the other electrode and the separator.