MXPA98009470A - Assemblies of elbow elbows and methods of production of the mis - Google Patents

Abstract

The present invention relates to wound electrode assemblies having conductive positioning lugs, to the wound electrode, and electrochemical cells employing such assemblies. In the process of the invention, the conductive positioning lug area of an electrode plate (1) coated with the active material is perforated with opposite, level, perforation plates (2) having raised surface probes (3) which penetrate the area of conductive positioning lug. The resulting area is classified from the active material, and a conductive positioning lug is welded to the treated area resulting in an electrode plate having a strongly integrated lug assembly.

Description

ASSEMBLIES OF WINDED ELECTRODES AND METHOD OF PRODUCTION OF THE SAME The invention relates to wound electrode assemblies having conductive positioning lugs, methods of attaching conductive positioning lugs to the wound electrode, and electrochemical cells employing such assemblies.

Electrochemical cells employing coiled electrode assemblies are widely known in the art. In "many of these cell structures the coiled electrode assembly is inserted into a composite housing which serves as the current conducting terminals for the cell.When this type of cell is assembled, a conductive positioning lug must first be secured to the cells. electrodes by an appropriate means such as welding.

Cells employing wound electrode assemblies can be produced using various electrochemical systems such as nickel metal hydride, nickel cadmium, nickel zinc and the like. When nickel metal hydride cells are used, the negative electrode of the nickel metal hydride cells is typically an electrode of REF .: 028893 storage of hydrogen in the form of a metal hydride. The positive electrode is typically nickel hydroxide. These cells also contain a separator and electrolyte, as is known in the art.

The positive electrode sheet is generally the outermost layer of the wound electrode for the nickel metal hydride cells and has a conductive positioning lug secured to a selected area of the electrified carrier at one end and to the housing of the cell at the opposite end . Before securing the conductive positioning lug, a selected area of the electrified carrier must be cleared from any active electrode material. Conventionally, this removal is by processes such as air jet, scraping, suction, ultrasonic clarification and the like. However, the use of these methods is the electrified carrier (substrate) dependent on the efficiency of removal of the active material from the substrate and the stress of the solder connection resulting from the locating lug to the substrate.

With the development of electrically conductive carriers made of felt, foam and other brittle substrates, the container for removing the active material from the substrate and attaching a positioning lug has become more difficult. Various methods have been used to break or loosen the active ingredient from the substrate, such as ultrasonic removal of the active material from the desired area, removal of the active material from the substrate along a total end of the electrode, attachment of the positioning lugs in the form a "t" or "v" or "h" to strengthen the lug area of positioning and others.

Although the removal of the active material from the total length of the electrode contributes to the elaboration of the efficiency of this type of cells, the current tendency is to maximize the capacity by reacting as much of the active material present in the electrochemical cell as possible. The need still exists for winding electrode assembly methods which removes substantially only a small section of the active material from the brittle substrates without weakening or damaging the substrates and which allow the attachment of a positioning lug to the substrates as well. clarified.

The present invention relates to winding electrode assemblies and production methods thereof. More specifically, the present invention relates to electrode plates used in wound electrode assemblies having a conductive positioning lug attached thereto. By treating the area of the positioning lug of an electrode plate coated with the active material in the manner described herein, the subsequent steps of the ultrasonic clarification removes substantially all of the active material present in that area. Ultrasonic welding of a conductive positioning lug to the area thus treated results in an electrode plate having a strong integrated positioning lug assembly.

The first step of the invention is a drilling step, wherein in opposition, the leveled drilling plates are pressed against the electrode plate in the conductive positioning lug area. The perforation plates have increased the surface probes which penetrate the active material and form a pattern of holes in the treated area. The next clarification step of the treated area results in a conductive positioning lug area substantially free of the active material. Using the process of the present invention, the various types of conductive positioning lugs could then be attached to the clarified area, resulting in a strong integrated positioning lug assembly.

It has also been found that the electrodes prepared by the process of the present invention are easier to assemble than the wound assemblies for use in electrochemical cells, due to a relatively flat positioning lug area. In addition, the process allows the incorporation of more active material in the finished electrochemical cell, resulting in greater capacity.

Figure 1 is a side view of an electrode plate in contact with the perforated plates having raised surface probes.

Figure 2 is a front view of a perforated plate having raised surface probes.

Figure 2a is a schematic side view of a raised surface probe of a perforated plate.

Figure 3 is a photograph showing a conductive spacing lug area of the electrode plate after a piercing step of the present invention.

Figure 4 is a photograph showing a conductive spacing lug area of the electrode plate after a piercing step of the present invention and ultrasonic clarification of the resulting area.

Figure 5 is a photograph of a conductive spacing lug area of the comparative electrode plate after the ultrasonic clarification of the positioning lug area without a piercing step of the present invention.

In the first step of the process of the present invention, the conductive positioning lug area of an electrode plate is pierced with opposing, leveling perforation plates having raised surface probes. In the next step, the resulting area is clarified from the active material exposed to an underlying layer of porous substrate substantially free of the active material. A conductive positioning lug is then attached to the underlying layer of the porous substrate.

Substrates useful in the preparation of positive electrodes in electrochemical cells made in accordance with this invention include any high porosity substrate having low mechanical strength such as foam, felt and the like. The substrates are coated with the active material for the desired electrochemical system.

In the case of metallic nickel hydrate cells, the active material of the positive electrode comprises one or a mixture of nickel compounds such as nickel hydroxide. The active material could also include other compounds, as is known in the art, including a conductivity improver such as cobalt oxide, a conductive material such as carbon black, a thickening agent, a binder, and the like. The metal powders and other components are mixed with water to form a wet suspension, which could be coated on the porous substrate by any of the known methods such as doctor's knives, roller coating, spray coating and the like. The coated substrate could then be dried and subjected to a smoothing process to form a smooth, hard electrode plate using means known in the art. The final thickness of the electrode plates is usually in the range of about 0.6 to 0.7 mm, preferably 0.63 to 0.67 mm. The electrode plates are then cut to the desired size for use in an electrochemical cell.

It has been found that by perforating the area of the conductive positioning lug with opposition, the perforated plates leveled, the conductive positioning lug area could be substantially cleared of the active material without damaging the fragile porous substrate of the underlying layer. The conductive positioning lug area to be clarified from the active material could be slightly larger than the width of the conductive positioning lug to be attached to the clarified area.

Figure 1 shows a front view of an electrode plate (1) in contact with the opposite perforation plates (2) in the perforation stage. The electrode plate (1) is subjected to a pressure of approximately 20 to 110 psi from the opposing piercing plates (2) having level raised surface probes (3) ending in a point. The raised surface probes are aligned such that when the opposing piercing plates are brought into contact in the electrode plate, the points of the raised surface probes (3) penetrate the surface of the porous substrate of the underlying layer without being in contact with one another. and another. In the most preferred embodiment, the raised surface probes penetrate the electrode plate by means of the substrate of the underlying layer but do not leave the opposite surface of the electrode plate.

Figure 2 shows a front view of a perforation plate (2) having level raised surface probes (3). The surface probes are leveled from the adjacent probes by a distance (4), and from the next row of surface probes by a distance (5), such that the opposing surface probes avoid being in contact between each other when pressed against the plate, electrode. As shown in Figure 2a, a schematic side view of a surface probe, the surface probes are preferably sharply angled (6), being less than 20 degrees, preferably 18 to 22 degrees from a line drawn perpendicular to the base of the probe superficial to the point of the test probe. The surface probes have a base (7) of approximately 0.4 mm and are approximately 0.6 ram in height (8), depending on the thickness of the electrode plate. The base and height of the surface probes could vary from these dimensions to avoid damaging the porous substrate of the underlying layer. For example, if narrower surface probes are used, the probes could exit the opposite side of the electrode plate without damaging the porous substrate of the underlying layer. If wider surface probes are used, the penetration depth of the surface probes in the electrode plate should be such that the porous substrate of the underlying layer is not damaged.

Figure 3 is a photograph of a conductive positioning ear area of the electrode plate that has been treated with the above-described piercing step of the present invention. The resulting area has diamond-shaped hole patterns on the surface of the electrode plate. Depending on the type of substrate and the thickness of the applied active material, one or more of the drilling steps could be used to facilitate the substantial removal of active material from this area during the next clarification step.

In the next stage of the process, the conductive positioning lug area is clarified from the active material using conventional means. In a preferred embodiment, the ultrasonic treatment is used to remove the active material. It is believed that the piercing step of the present invention also decreases the amount of ultrasonics needed to substantially remove the active material from the treated area, resulting in less damage to the brittle substrate of the underlying layer. The type of equipment used to apply ultrasonics to the treated area varies and typically includes an ultrasonic horn that has either smooth or raised surfaces and an anvil that has either smooth or raised surfaces. In a more preferred embodiment of the present invention, the ultrasonic horn has a smooth surface and the anvil consists of a movable pulley with raised surfaces that have diamond-shaped smooth points to prevent damage to the substrate. The amount of ultrasonics applied is typically in the range of at least about 20 kHz to 100 percent amplitude (about 20 kilojoules of energy) for a duration of about 0.5 to 1.0 second.

Figure 4, a photograph of a conductive positioning lug area with the piercing step of the present invention and followed by an ultrasonic clarification step, shows a porous underlying layer substrate substantially free of the active ingredient in the lug area of conductive positioning. The photograph shows the integrity of the fragile substrate that remains in tact.

Figure 5, a photograph of a comparative method in which the conductive positioning lug area is clarified using only ultrasonic clarification without the piercing step of the present invention, shows damage to the fibers of the porous, brittle substrate of the underlying layer . Ultrasonic clarification of the conductive positioning lug area without the use of at least one drilling step of the present invention destroys the ability to weld a conductive positioning lug to the conductive positioning lug area area to be clarified from the substrate.

After removal of the active material from the treated area, a conductive positioning lug could be attached to the substrate using resistance or ultrasonic welding. The conductive positioning lug could be nickel or electroplated steel with nickel, and could be any desired shape such as a double layer positioning lug (h-shaped vo) or a rectangular single layer positioning lug. flat In a preferred embodiment of the present invention, a rectangular single-layer positioning tab is attached to the substrate using ultrasonic welding. Ultrasonic welding is performed using means known in the art. In a preferred embodiment, the ultrasonic horn has raised surfaces and the anvil has a flat surface. To form a friction weld between the substrate and the conductive positioning lug, the ultrasonic vibrations are applied at 20 kHz and 100 percent amplitude in a parallel direction (180 degrees) to the surfaces to be welded, with a weld pressure of approximately 30 psi. Depending on the type of conductive positioning lug to be used, the welding energy could be in the range of about 18 joules for a single layer positioning lug to about 30 to 45 joules for a double layer positioning lug; with a welding time of approximately 0.5 to 1 second.

In a preferred embodiment of the present invention, a single layer conductive positioning lug is bonded to the brittle clarified substrate using an ultrasonic horn having a raised surface and an anvil having a flat surface. It is unexpected that a single-layer conductive positioning lug and a coiled fragile substrate form a sufficient friction weld using a flat anvil. Typically, ultrasonic welding of a conductive positioning lug to a fragile substrate involves the use of a double layer conductive positioning lug, such as a h-shaped lug or a v-shaped lug. These dual layer positioning lugs facilitate the use of an anvil having raised surfaces and an ultrasonic horn having raised surfaces because the substrate overlaps between the two metallic layers and is not in contact with the ultrasonic horn or the anvil. The use of an anvil having raised surfaces would destroy the exposed brittle fibers of the substrate when soldered to a single layer conductive positioning lug. It has been found that using the methods of the present invention, all forms of positioning lugs could be successively welded to the brittle, porous conductive positioning surface of a substrate using a flat anvil.

The positive electrode having a connected conductive positioning lug as described above, could then be processed using conventional steps. These steps could include providing a hole in the positioning lug above the electrode edge to improve flexibility and facilitate attachment of the positioning lug of the cell cap; and / or tape coating the conductive positioning lug and the conductive positioning lug area to ensure additional resistance of the weld and to avoid internal shorts.

The ability to use a single-layer conductive positioning lug as opposed to a double-layer conductive positioning lug provides improvements in commercial manufacturing processes by eliminating an elevated area which is normally associated with wound-up electrode assemblies having a double layer positioning lug (eg double thickness). The removal of this raised area also reduces the possibility of internal shorts, and allows for the use of additional layers of electrodes to be incorporated into wound electrode assemblies.

The following examples compare the results of ultrasonic welding and conventional resistance welding using the methods of the present invention. The positive electrodes are prepared by wet suspension of the desired ingredients (nickel hydroxide, cobalt oxide, gelatinising agent, binder and carbon black) on electroplated nickel foam substrate weighing between approximately 320 m2 / - fa approximately 500 m2 / g, such as Eltec 400 foam from Eltec, Inc. The coated substrate is then dried at about 110 to 120 degrees Centigrade and smoothed using pressures between about 30 to 40 tons to form the positive electrode plates. The positive electrode plates are then cut to the desired size. A series of non-piercing electrode plates are prepared using one or more drilling steps of the present invention, to form a treated conductive positioning ear area. The conductive positioning lug area is then clarified using ultrasonic clarification with an ultrasonic horn having a smooth surface and a movable wheel anvil having raised surfaces.

A single-layer conductive positioning lug is then joined to the clarified area using ultrasonic welding. Ultrasonic welding is carried out using an ultrasonic horn having raised surfaces and an anvil having a smooth surface. Using conventional resistance welding, a dual layer positioning lug is attached to a second series of electrode plates prepared as described above.

The strength of the lug welds are measured using a standard tensile test on a Traction Tester from Lloyd Instruments, Model LXR. The test is run by holding one end of the assembled tester to the conductive positioning lug, and the other end to the base of the electrode plate. The fasteners are then pulled in opposite directions at a speed of 5 mm per minute until the connection between the positioning lug and the electrode plate reaches the maximum force before weakening the solder of the conductive positioning lug / substrate. The results are reported in Table l.

A comparative example was run using an electrode plate which has been clarified without using a piercing step of the present invention. A single-layer conductive positioning lug could not be welded to this electrode plate using ultrasonic welding due to damage to the underlying layer of the substrate and incomplete clarification of the active material from the conductive positioning lug area. The results are shown in Table 1 below. Each sample identification represents an average result for five samples from five different batches, using identical processing steps.

Table 1. Traction Test Sample Ultrasonic Welding Welding with / tape (kg) resistance with / tape. (kg) A 0.7 0.71 B 0.71 0.66 C 0.77 0.62 D 0.7 0.84 Comparative without / possible welding The results show consistent weld strength when a single layer conductive positioning lug is joined using the process of the present invention. In addition, the process of the present invention provides single layer / substrate positioning solder resistance comparable to those using single layer / substrate positioning lug resistance welds. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (15)

1. A process for producing an electrode plate having a conductive positioning area, characterized in that it comprises the steps of: to . piercing an area of an electrode plate with opposite, level, piercing plates having raised surface probes. b. clarifying the resulting area to expose a porous, underlying layer substrate to form a conductive positioning lug area; Y c. attaching a conductive lug to the underlying layer porous substrate.

2. The process of claim 1, characterized in that it also comprises more than one perforation stage.

3. The process of claim 1, characterized in that the clarification step is applying ultrasonics to the resulting area.

4. The process of claim 3, characterized in that the ultrasonics are applied by an ultrasonic horn having a smooth surface and an anvil having raised surfaces.

5. The process of claim 4, characterized in that the anvil comprises a movable pulley anvil.

6. The process of claim 1, characterized in that the exposed underlying layer porous substrate is substantially free of the active material after said clarification step.

7. The process of claim 1, characterized in that the joining step is applying ultrasonic.

8. The process of claim 7, characterized in that the ultrasonics are by an ultrasonic horn having raised surfaces and an anvil having a smooth surface.

9. The process of claim 1, characterized in that the conductive positioning lug is made of nickel or electroplated steel with nickel.

10. The process of claim 1, characterized in that the conductive positioning lug is a single-layer conductive positioning lug.

11. The process of claim 1, characterized in that the conductive positioning lug is a double layer conductive positioning lug.

12. The process of claim 1, characterized in that it comprises the step of drilling a hole in the conductive positioning lug.

13. The process of claim 1, characterized in that it further comprises the step of coating with tape the conductive positioning lug and the conductive area.

14. An electrode plate having an underlying layer porous substrate coated with an electrochemically active material, characterized in that the electrode plate comprises a conductive positioning lug area substantially free of the active material and a conductive positioning lug attached to the lug area of the electrode plate. conductive positioning.

15. An electrochemical cell, comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that the positive electrode comprises a porous underlying layer substrate coated with an electrochemically active material, wherein the electrode plate has a lug area of free conductive positioning of the active material and a conductive positioning lug attached to the conductive positioning lug area.