JP2899318B2 - Alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an alkaline storage battery such as a nickel-cadmium battery or a nickel-metal hydride battery having a hydrogen storage alloy as a negative electrode.

(Prior Art) As an electrode used in an alkaline storage battery, a so-called sintered body manufactured by impregnating and chemically forming an aqueous solution of an active material on a substrate obtained by molding and sintering carbonyl nickel, for example, is conventionally used. Method was used. However, such a sintered electrode requires a very complicated operation in the steps of producing a sintered substrate and impregnating the active material, and thus has a problem of poor mass productivity.

Therefore, as an alternative to the sintering method, the powdered active material is pasted with a suitable solvent and binder,
A so-called paste-type electrode has been proposed in which this paste-like material is formed by filling a three-dimensional mesh-like porous body such as a sponge-like nickel or a sintered body of nickel short fibers, and a part thereof has been put into practical use. The paste method has a simpler manufacturing method than the sintering method, so that the productivity can be significantly improved.

However, in an alkaline storage battery formed by winding an electrode in which a paste-like material is filled in a three-dimensional mesh-like porous body and a counter electrode with a separator interposed therebetween, the battery may cause an internal short circuit immediately after winding or at the time of initial filling after battery assembly. There was a problem that it was easy to get up. Many of the causes of the internal short-circuit occur because the outer peripheral side of the three-dimensional mesh-like porous body exposed from the end face of the paste-type electrode at the beginning of winding breaks through the separator and reaches the counter electrode. The paste type electrode, unlike the sintered type electrode, because the substrate is a three-dimensional mesh porous body having a high porosity, the pressure applied to the substrate at the time of winding is larger than that of the sintered type electrode, as a result, In particular, there is a disadvantage that the separator easily breaks through the edge portion of the side end face.

As means for preventing the above-described problems, there are a method of attaching an adhesive tape to the side end surface of the paste-type electrode and a method of applying a curable resin such as an epoxy resin, but any method reduces mass productivity. Not only that, the performance of the electrode is impaired, so that it has not been put to practical use.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned conventional problems, and an object of the present invention is to provide an alkaline storage battery which is excellent in mass productivity and has improved internal short circuit failure.

[Constitution of the Invention] (Means for Solving the Problems) The present invention relates to a method of winding a paste-type electrode comprising a three-dimensional net-like porous substrate holding a paste-like material and a counter electrode with a separator interposed therebetween. In the alkaline storage battery provided with the electrode group formed by turning, the side end surface of the paste-type electrode at the beginning of winding is curved.

As the paste-like material, for example, nickel as a main component, an active material containing a cobalt compound or a cadmium compound as needed, carboxymethyl cellulose,
Examples thereof include those obtained by mixing a binder such as methyl cellulose with a dispersant such as water.

Examples of the three-dimensional mesh-like porous body constituting the substrate include sponge-like nickel and a sintered body of nickel short fiber.

As a method for forming the side end surface of the paste-type electrode at the beginning of winding into a curved shape, for example, the beginning of winding of the electrode is cut using a die having a tapered or round shape, and the cut surface is formed into a curved shape. And the like.

(Operation) As already described in the prior art, in an alkaline storage battery formed by winding a paste-type electrode in which a paste-like material is filled in a three-dimensional net-like porous body with a separator interposed therebetween, immediately after winding, or assembling the battery The cause of the occurrence of an internal short circuit at the time of the initial filling later is mainly due to the fact that the outer peripheral side of the three-dimensional mesh-like porous body exposed from the end face of the paste electrode breaks through the separator and reaches the counter electrode to make contact therewith.
This is because most of the force applied to the winding start portion of the paste electrode is concentrated on the side end surface, and since the side end portion has an edge shape, the force is received as a line or a point. Because it breaks through.

For this reason, the present invention provides a paste-type electrode having a curved end surface at the beginning of winding, and winding the paste so that the curved surface of the side end faces the counter electrode with a separator interposed therebetween. Can be applied as a surface. As a result, the force applied to the separator per unit area at the beginning of winding of the paste electrode can be reduced, so that an internal short-circuit failure such as breaking through the separator and reaching the counter electrode and making contact can be prevented.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment FIG. 1 is a cross-sectional view of an alkaline storage battery showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a metal can also serving as a negative electrode terminal.
An electrode group 2 is accommodated in the metal can 1.

The electrode group 2 was manufactured by the following method: a paste obtained by kneading an active material composed of nickel hydroxide and cobalt hydroxide with carboxymethylcellulose and water as a three-dimensional net porous body. The paste was filled, dried, and pressed to produce a paste electrode body. Subsequently, as shown in FIG. 2, the paste-type electrode body 21 is cut by a lower mold 22 and an upper mold 24 in which a cutting portion 23 is formed in a round shape, and the winding start side end face 3a shown in FIG. The paste-type positive electrode 3 having a curved shape was obtained. The positive electrode 3
Is provided with a tab 4. Next, as shown in FIG. 4, the pasted positive electrode 3 and the cadmium negative electrode 5 serving as a counter electrode and the curved surface side of the winding start side end 3a of the positive electrode 3 with the separator 6 interposed therebetween face the cadmium negative electrode 5 with the separator 6 interposed therebetween. The electrode group 2 was manufactured by spirally winding as described above.

A sealing plate 8 serving as a positive electrode terminal having a hole 7 in the center is supported and fixed via an insulating gasket 9 at the upper opening of the metal can 1. The sealing plate 8 is provided with an explosion-proof mechanism including a safety valve 10 and a cap 11 for holding the safety valve 10. In addition, the negative electrode 5 of the electrode group 2 is connected in direct contact with the inner surface of the metal 1 also serving as the negative electrode terminal, and the paste-type positive electrode 3 is connected via a tab 4 to a sealing plate 8 also serving as the positive electrode terminal. I have.

Comparative Example As shown in FIG. 5, an electrode manufactured by spirally winding a paste-type positive electrode 3 having an edge-shaped outer peripheral end 3a 'at the beginning of winding together with a negative electrode 5 as a counter electrode with a separator 6 interposed therebetween. An alkaline storage battery having the same structure as that of the example except that the group 2 'was used was assembled.

Thus, 100 alkaline storage batteries of the present example and the comparative example were prepared, and the internal resistance was measured before the first charge, then the first charge was performed, and the battery voltage was measured. The number was checked. As a result, in this example, the internal short-circuit failure out of 100 pieces was zero. On the other hand, in the comparative example, 24 out of 100 internal short-circuit defects were observed. This corresponds to the edge of the paste type positive electrode 3 in the electrode group 2 'shown in FIG.
3a 'breaks through the separator 6 and comes into contact with the cadmium negative electrode 5.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an alkaline storage battery having extremely few defects due to an internal short circuit and having excellent productivity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an alkaline storage battery showing one embodiment of the present invention, FIGS. 2 to 4 show manufacturing steps of an electrode group incorporated in the alkaline storage battery of FIG. 1, and FIG. FIG. 3 is a perspective view showing the paste-type positive electrode after cutting, and FIG. 4 is a schematic view showing an electrode group. FIG. 5 is a schematic diagram showing an electrode group of a comparative example. DESCRIPTION OF SYMBOLS 1 ... Metal can, 2 ... Electrode group, 3 ... Positive electrode, 3a ... Curved winding start side end face 5 ... Cadmium negative electrode, 6
... separator, 8 ... sealing plate, 9 ... insulating gasket.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiro Yoshida 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation (72) Inventor Hiroyuki Hasebe Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa No. 1 Toshiba Research Institute, Inc. (72) Kunihiko Sasaki Inventor, No. 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-57-43361 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 4/24 H01M 10/28

Claims (1)

(57) [Claims] 1. An alkaline storage battery comprising an electrode group formed by winding a paste electrode formed of a three-dimensional net-like porous substrate holding a paste and a counter electrode with a separator interposed therebetween. An alkaline storage battery, wherein a side end surface of the paste-type electrode at the beginning of winding is a curved surface.