Galvanic element with a set of wound electrodes

A galvanic element including at least one positive electrode in strip form, at least one negative electrode in strip form, at least one separator in strip form interposed between the positive and negative electrodes such that the separator and the electrodes are spirally rolled, and at least one disk-shaped current collector connected mechanically and electrically conductively to an edge portion of at least one of the electrodes, the current collector having more than one contact tab.

RELATED APPLICATION

This application claims priority of German Patent Application No. DE 101 44 281.5, filed Sep. 8, 2001.

FIELD OF THE INVENTION

This invention relates to a galvanic element with a set of wound electrodes. More particularly, this invention relates to lithium, nickel-metal hydride, nickel-cadmium and other galvanic elements in cylindrical cell form with a set of wound electrodes.

BACKGROUND

DE 25 16 530 C3 discloses a current collector in the form of a thin metal plate with a contact tab which has a surface with convex elevations in the form of points, punched formations or a wire mesh.

Another current collector with radially running apertures according to DE 30 19 186 C2 has a contact tab which is beveled and angled away on its longitudinal sides, is bent back toward the current collector and, once it has been firmly connected to the current-dissipating inner side of the cell cover and the cover has been closed, is resiliently supported by the integrally formed webs against the collector plate.

U.S. Pat. No. 4,554,227 attempts to lower the transition resistance by various shaped sheet-metal parts with a contact tab, by forming as many linear contacts as possible.

The configuration of the current collector for wound electrodes with a contact tab as provided by the prior art represents a constriction for the current conduction which can only be eliminated to a restricted extent by the choice of material and dimensioning.

In the case of the solution found in EP 0 822 605 B1, a plurality of contact tabs which are distributed over the length of the strip are welded onto the edges kept free of active material.

The construction described in EP 0 298 800 B1 has contact tabs fastened transversely over the entire width of the strip and wound up with it.

In EP 0 357 399 B1, the edge of the electrode in strip form is slit into individual tongues which, after winding, are folded together and connected by a metal pin.

Such contact tabs fastened to or on the electrode strip or formed by the electrode strip already prove to be disruptive during winding of the electrode and reduce the production capacity of the winding machines.

The embodiment according to EP 0 413 867 B1 combines a plurality of current collectors each with a contact tab in a segmented or nested fashion which are grouped around an opening in the center of the arrangement of collectors. This construction has the disadvantage that it is heavy and complex to assemble. In the embodiment represented, no more than two contact tabs or stacks of contact tabs can be realized.

It would accordingly be advantageous to provide a galvanic element with a set of wound electrodes in which arrangement connecting elements that are easy to assemble, inexpensive and nevertheless can withstand high current loads ensure reliable contacting of the wound electrodes with the poles of the galvanic element.

SUMMARY OF THE INVENTION

This invention relates to a galvanic element including at least one positive electrode in strip form, at least one negative electrode in strip form, at least one separator in strip form interposed between the positive and negative electrodes such that the separator and the electrodes are spirally rolled, and at least one disk-shaped current collector connected mechanically and electrically conductively to an edge portion of at least one of the electrodes, the current collector having more than one contact tab.

DETAILED DESCRIPTION

It will be appreciated that the following description is intended to refer to specific embodiments of the invention selected for illustration in the drawings and is not intended to define or limit the invention, other than in the appended claims.

The galvanic element according to the invention offers the least possible resistance to the electrical current through the current collectors with more than one contact tab. These current collectors are much easier to assemble than known collector constructions in galvanic elements for high-current applications. The space-saving flat design of the current collectors results in a high utilization of the capacity of the galvanic element. The invention can accordingly be used with preference in the case of lithium, nickel-metal hydride, nickel-cadmium and other galvanic elements in a substantially cylindrical cell form with wound electrodes.

One special advantage of the invention is that a high-capacity current collector system with a low electrical resistance at the positive and negative electrodes of an electrode coil is realized with the same component. For this purpose, one or more current collectors are conductively connected to the positive and negative edges at the end faces of the wound electrodes.

The contact tabs of the current collector of the one wound electrode are bent inwardly at the edge of the current collector, so that the contact tabs do not touch the housing cup after the galvanic element has been fitted. The end of each contact tab is preferably bent outwardly in a Z-shaped manner and is connected mechanically and electrically conductively to the electrically conducting cover, for example, by welding or pressing.

The contact tabs of the current collector of the other electrode, which is to be inserted into the housing cup, are bent around in such a way that they lie against the lateral surface of the electrode coil. After insertion, the contact tabs lie over a large surface area against the inner lateral surface of the housing cup and, consequently, ensure optimum current transmission from the wound electrode to the housing cup.

To achieve an optimum connection between the current collector and the edges of the set of wound electrodes, it is advantageous if the current collectors are embossed and, as a result, have pimples (FIG. 8(a)), points (FIG. 8(b)), burrs (FIG. 8(c)) or the like on their surface.

An improvement in the connection between the current collector and the edges of the wound electrodes can also be achieved by the current collector being embossed with radially running beads (FIG. 8(d)). A further possibility of improving this contact is to provide the current collector with apertures.

Turning now to the drawings, and referring toFIG. 1a, a collector disk1is connected mechanically and electrically conductively, for example, by welding or pressing to the edge portion of an electrode of the set of wound electrodes4, held together by a winding band5.FIGS. 6 and 7show positive electrode40, negative electrode41and separator42as they are arranged in a sprial wound or rolled form.FIG. 1bshows a plan view of the arrangement represented inFIG. 1a, in which the embossed structures3of the current collector represented by way of example can be seen. InFIG. 1cand the plan view ofFIG. 1d, the contact tabs2are bent in a Z-shaped manner inwardly and then outwardly, in the way represented in detail inFIG. 1f. InFIG. 1e, the ends of the contact tabs are connected mechanically and electrically conductively, preferably by welding or pressing, to the cell cover6, which is provided on the peripheral edge with an electrically insulating seal10.

According toFIG. 2a, a collector disk1is connected electrically conductively and mechanically to the edge of the other electrode of the electrode coil4.FIG. 2bshows a plan view of the arrangement represented inFIG. 2a, in which the embossed structures or apertures3of the current collector given by way of example can be seen. InFIG. 2cand the plan view ofFIG. 2d, the contact tabs2are bent around in the direction of the lateral surface of the set of wound electrodes4.

According toFIG. 3a, as an alternative, two contact disks1a,1b, preferably turned with respect to each other about a contact tab division and placed one on top of the other, are connected electrically conductively and mechanically to the edge of the other electrode of the set of electrodes4, to reduce electrical resistance still further.FIG. 3bshows a plan view of the arrangement represented inFIG. 3ain which the embossed structures3of the current collector given by way of example can be seen. InFIG. 3cand the plan view according toFIG. 3d, the contact tabs2a,2bare bent around in the direction of the lateral surface of the set of wound electrodes.

According toFIG. 4, the set of electrodes4pre-assembled with the current collectors1,1a,1band with the cover6with seal10is pushed by a pushing-in tool8into the housing cup7held by the cup holder9.

FIG. 5shows the ready-assembled galvanic element, in which the housing cup is closed by flanging around the edge of the cup, which is provided with a valve plug with an electrically conducting cap11. The set of wound electrodes4with binding band5can be seen inside the electrically conducting cup-shaped housing7. The electrically conducting cover6is sealed with respect to the housing by an electrically insulating seal10. One or more current collectors1,1a,1bwith a plurality of contact tabs2,2a,2barranged on them in a radially distributed manner form the connecting elements which conductively bridge the spatial distance between the poles of the galvanic element, which are formed by the cover6and the housing7, and the edge of the set of wound electrodes4.