JPS594541Y2 - flat battery - Google Patents

Description

[Detailed description of the invention] The present invention relates to a flat battery using electrodes that swell due to a discharge reaction, such as a non-aqueous electrolyte battery, and its purpose is to reduce the discharge capacity due to lack of electrolyte. The purpose is to prevent the decline.

FIG. 2 shows the structure of a conventional flat non-aqueous electrolytic battery.

In the figure, 11 is a battery container, and a manganese dioxide positive electrode 12 is disposed on the inner bottom surface of the battery container.

Reference numeral 14 denotes a sealing lid which has an insulating backing 15 supported by the peripheral edge 12' of the positive electrode 12 on its periphery, and a negative electrode 17 made of a rolled lithium plate is crimped onto the inner bottom surface of the insulating backing 15. It is caulked by the edges.

18 is a separator impregnated with electrolyte. As shown in the equation below, the discharge of this battery is a reaction in which lithium in the negative electrode becomes ions, dissolves, diffuses, and enters the positive electrode to form a compound.

MnO2+Li→Mn02(Li)・----・■Thus, as the discharge reaction progresses, the negative electrode volume decreases and the positive electrode volume increases, and the volume change at this time is larger for the positive electrode. The separator interposed between the positive and negative electrodes is compressed, and the electrolyte held in the separator is squeezed out. As a result, the internal resistance between the positive and negative electrodes increases, making it impossible to obtain sufficient discharge capacity and shortening the battery life. You will end up getting stuck.

As a countermeasure to this problem, a structure has been proposed in which an electrolytic solution holding layer is disposed on the back surface of the positive electrode, but in this case, the diffusion of the electrolytic solution to the reaction surface is delayed, so that a sufficient effect cannot be obtained.

In addition, in the conventional battery structure shown in FIG.
The peripheral edge 12' of the negative electrode 17 is
Since it is shielded from the periphery 12', it is difficult to discharge, and even after the discharge is completed, this peripheral edge 12' tends to remain in an undischarged state.

The present invention was developed by focusing on the above-mentioned phenomenon, and involves removing the peripheral part of the positive electrode that is difficult to discharge, and placing a liquid holder having sufficient mechanical strength to support the insulating backing in this part. This prevents a decrease in discharge capacity due to electrolyte shortage.

Hereinafter, one embodiment of the present invention will be explained based on the drawings. In Fig. 1, 1 is a battery container which also serves as a positive electrode terminal, and 2 is a positive electrode having a smaller diameter than the battery container 1 and using manganese dioxide as an active material, which is located inside the container. Pressure molded on the inner bottom surface.

Reference numeral 3 denotes a liquid holding body which is the gist of the present invention, and is made of a molded body of graphite powder and is disposed in the gap between the battery container and the positive electrode.

Reference numeral 4 denotes a sealing lid having an insulating backing 5 supported by the liquid holder 3 disposed around its periphery, and a negative electrode 7 made of a rolled lithium plate crimped onto a negative electrode current collector 6 fixed to the inner bottom surface,
The bent edges of the battery container are caulked and attached via an insulating backing 5.

Reference numeral 8 denotes a separator interposed between the positive and negative electrodes, which is made of polypropylene nonwoven fabric and is impregnated with a non-aqueous electrolyte.

According to the battery structure of the present invention, since the liquid retainer is disposed at the periphery of the positive electrode, even if the amount of electrolyte decreases on the reaction surfaces of the positive and negative electrodes as the discharge reaction progresses, the electrolyte is supplied sequentially. This method is effective because it suppresses a decrease in discharge capacity due to shortage, and the electrolyte can be supplied to the reaction surface without delay compared to the case where a liquid retaining layer is provided on the back surface of the positive electrode as described above.

The liquid holding body may be any material as long as it has mechanical strength to support the insulating backing, and in addition to the graphite powder molded body shown in the examples, metal powder molded bodies such as carbon, nickel, aluminum, copper, etc., or alumina , an inert powder molded body such as silica gel can be used.

However, a metal powder molded body is preferable in consideration of electroconductivity in addition to liquid holding power and mechanical strength.

As mentioned above, the present invention relates to the improvement of a flat battery equipped with an electrode that swells due to a discharge reaction.The present invention focuses on the fact that the peripheral part of the positive electrode, which is shielded from the negative electrode by an insulating backing, is less likely to be discharged, and eliminates this peripheral part. By placing a liquid holder in this area, the electrolyte can be smoothly supplied to the reaction surface, preventing a decrease in discharge capacity due to lack of electrolyte, and improving the utilization rate of the positive electrode. Therefore, its practical value is extremely large.

Note that the present invention is not limited to the non-aqueous electrolyte batteries shown in the examples, but includes, for example, silver batteries and mercury batteries, in which the electrode swells as the discharge reaction progresses, and the electrolysis that is interposed between the electrode and the counter electrode swells. This can be applied to battery systems in which discharge capacity decreases due to electrolyte shortage due to liquid being squeezed out.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a flat battery according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a conventional battery. 1...Battery container, 2...Positive electrode, 3...
...Liquid retainer, 4...Sealing lid, 5...
...Insulating backing, 7...Negative electrode, 8...
...Liquid impregnated separator.

Claims (1)

[Claims for Utility Model Registration] ■ Consisting of a powder molded body in which an electrode, which is smaller in diameter than the container and swells due to the discharge reaction, is arranged on the inner bottom surface of the battery container, and an insulating backing can be supported in the gap between the container and the electrode. A flat battery, in which a liquid holding body is disposed, and a sealing lid is sealed via an insulating backing supported by the liquid holding body by a bent edge of the battery container that houses the electrode, separator, and counter electrode. . (2) The flat battery according to claim (2), wherein the powder molded body is a conductive powder molded body.