AU4355999A - Electrode assembly - Google Patents

Description

WO00/00671 PCT/CA99/00590 TITLE: ELECTRODE ASSEMBLY FIELD OF THE INVENTION The present invention is directed to an electrode 5 assembly for use in electrical apparatus, in particular where the electrode assembly is a monopolar multi-plate electrode assembly with the individual electrode plates of the same polarity connected together by a bridging strap contiguous with each of the interconnected electrode 10 plates. BACKGROUND OF THE INVENTION Various configurations of electrode assemblies are used in a number of different electrical apparatuses. Such 15 electrical apparatus include multi-plate storage batteries, electrolysis and other electrochemical cells. Electrode assemblies may be either monopolar or bipolar depending upon the nature of the electrical apparatus and the required properties of the electrode assembly. Bipolar 20 electrode assemblies have a plurality of individual plates with the opposite sides of each of the plates carrying the positive and negative charges. Another type of electrode assembly is a monopolar electrode assembly which has positive and negative electrode plates interleaved with one 25 another. Monopolar electrode assemblies are commonly utilized in storage batteries and electrolysis and other electrochemical cells. Depending upon the application, the electrode plates may be separated by electrolyte, or the electrode assembly may be provided with electrically inert 30 separators, such as glass mat separators, commonly utilized in lead acid storage batteries. Monopolar electrode assemblies are provided with connectors on the outside plates of the assemblies for 35 connecting the electrical apparatus into electrical circuits. Bipolar electrode assemblies require that in addition to the connectors on the outside plates of the assembly, the individual anodes or cathodes are charging the surfaces through the electrolyte. For monopolar 40 assemblies, most commonly, the anodes or cathodes are WO00/00671 PCT/CA99/00590 interconnected together by providing a lug at an upper corner of the electrode plate, the lugs being interconnected by a busbar or by fusing or welding the lugs together. This interconnection or fusing of the lugs 5 results in connector junctions, which require additional steps in the manufacturing process. In addition, connector junctions may cause local increases in current density in the connector junction, potentially reducing the efficiency of the electrode assembly. 10 SUMMARY OF THE INVENTION In one aspect, the present invention is directed to an assembly of monopolar electrodes for use in electrical apparatus. The electrode assembly comprises a pair of 15 electrodes, each of the electrodes having a plurality of spaced apart electrode plates connected together inline. The electrode plates of each of the electrodes are connected to the next electrode plate in the series by a bridging member contiguous with each of the interconnected 20 electrode plates. In another aspect of the invention, there is provided an electrode for use in an electrode assembly. The electrode comprises a plurality of parallel spaced 25 apart electrode plates connected in series. Each of the electrode plates is connected to the next plate in the series by a bridging strap contiguous with each of the interconnected electrode plates. 30 BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are shown in the drawings, wherein: Figure 1 is a perspective view of an electrode assembly according to the present invention; 35 Figure 2 is a plan view of an electrode for use in the electrode assembly of Figure 1; and Figure 3 is a perspective view, partly in cross section of an electrolysis cell utilizing the electrode assembly of Figure 1. 40 - 2 - WO00/00671 PCT/CA99/00590 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an electrode assembly according to the present invention is illustrated in the figures, generally indicated by the numeral 10. Electrode 5 assembly 10 illustrated in the figures is an assembly of two monopolar multi-plate electrodes made up of an anode 12 and a cathode 14. The electrode assembly 10 illustrated in the figures is of particular use in an electrolysis cell for generation of hydrogen gas, although, as explained 10 below, the electrode assembly 10 can be used in other types of electrical apparatuses. Each of the individual electrodes, anode 12 and cathode 14 are made up of spaced apart inter-connected 15 electrode plates 16 and 18. The electrode plates 16 and 18 of the anode 12 and cathode 14 are interconnected to one another by bridging members 20 and 22 respectively contiguous with and connecting together the individual electrode plates 16. Thus anode plates 16 are 20 interconnected by bridging members 20 at a lower edge of the anode plates 16. Similarly, the individual cathode plates 18 are interconnected by bridging members 22 located at an upper edge thereof. 25 Figure 2 illustrates a plan view of an individual electrode for use in the electrode assembly 10. The electrode illustrated is an anode 12, however, the cathode 14 is similarly constructed. The individual electrode is formed from a metal blank of a suitable metal material by 30 removing sections of the metal blank to provide for the series of electrode plates 16 interconnected together by the bridging members 20. For use in an electrolysis cell for generation of hydrogen gas, the metal used for construction of the electrodes is preferably a suitable 35 stainless steel, most preferably nickel plated stainless steel. The selection of the suitable metal for use in other applications or other electrical apparatuses would be readily apparent to those skilled in the art. - 3 - WO00/00671 PCT/CA99/00590 Once the electrode 12 is formed, it is bent into an accordian shape to provide the parallel spaced apart electrode plates 16 for the individual electrode. As set out in the figures, one of the electrodes has the bridging 5 members 20 located along the edge adjacent the top, while the other electrode has the bridging members 22 located along the edge adjacent the bottom. The two individual electrodes are then interleaved by sliding one electrode into the other with the plates of the first electrode 10 passing between the plates of the second electrode. Once the two electrode plates are interleaved, they may be held in the proper position and spacing by use of a cartridge to hold the electrodes. The cartridge may be provided by using spacer blocks to hold the upper and/or lower ends of 15 the electrode plates in position the spacer blocks being joined to one another by a suitable means such as bolts and nuts. The spacer blocks, bolts and nuts are constructed of a suitable non-conducting material, which is resistant to the physical and chemical environment of the electrical 20 apparatus in which the electrode assembly is to be used. Preferrably, for an electrolysis cell, the spacer blocks, bolts and nuts are polypropylene. The details of an electrochemical cell 50 25 utilizing an electrode assembly of the present invention are shown in Figure 3. The electrochemical cell 50 is an electrolysis cell utilized in a hydrogen generating system to generate small quantities of hydrogen and oxygen with the hydrogen and oxygen generated then being combined with 30 the usual air/fuel mixture to improve the efficiency of internal combustion engines. A typical such hydrogen generating system includes the electrolysis cell 50 for generating hydrogen and oxygen gases by electrolysis of an aqueous solution, a power source for providing electrical 35 power to the electrolysis cell, an outlet flow means for introducing the generated gases into the intake manifold system of an internal combustion engine, a monitoring means for monitoring the operating conditions of the hydrogen generating system, and a control means connected to the 40 monitoring means for controlling the operation of the - 4 - WO00/00671 PCT/CA99/00590 hydrogen generating system in response to the monitoring means. One such hydrogen generating system as described in co-pending Canadian patent application number 2,209,237 includes an electrolysis cell 10 which is used to generate 5 the hydrogen and oxygen gases by electrolysis of a suitable aqueous medium. In the system described, the gases generated by the electrolysis cell are fed through a moisture trap which is connected to the cell by a suitable tubing which is provided with a check valve to prevent the 10 back flow of fluids into the electrolysis cell . The output of the moisture trap is connected to a bubbler by means of a suitable tubing which is also provided with a check valve to prevent back flow of fluids. From the bubbler the gases flow through tubing to a filter to remove any particulate 15 material or residual moisture in the gases. From the filter the gases flow through tubing to a flow control valve which is adjustable to regulate the flow of the gases. The output of the flow control valve is connected to a pump which pumps the gases to a suitable part of the intake system of 20 the engine. Electrochemical cell 50, preferably has a cylindrical shaped case 52, constructed of a suitable material which would be inert to the electrolyte solution 25 and would not be affected by the voltages or temperatures encountered in the electrolysis cell 50. The case 52 should also preferably have a co-efficient of expansion, which does not cause significant expansion of the dimensions of the cell 50 under the operating conditions of 30 the hydrogen generating system. Preferably, the case 52 of the electrolysis cell 50 is a polyvinyl chloride. While the case 52 may be provided as a one-piece mold, it is preferred that for uniformity, the case 52 be in two sections, the sidewall 54 and the base 56 which are PVC 35 welded to give the characteristics of a one-piece structure. The electrochemical cell 50 is provided with a welded on cap 58, which represents a gas accumulation zone. 40 The cap 58 is provided with a first opening 60 for an - 5 - WO00/00671 PCT/CA99/00590 outlet of the electrolysis cell 50 to which tubing for the generated gas is connected. Cap 58 is provided with a second opening 62 for receiving a fill plug 64. Fill plug 64 is utilized to allow the addition of distilled water or 5 electrolyte solution to the cell 50 as the level of fluid in the electrolysis cell 50 decreases. Fill plug 64 may also incorporate a pressure release mechanism to provide for relief of the pressure within the cell 50 should the interior pressure increase beyond a set limit. The fill 10 plug 64 may also function as a rupture plug. In case of malfunction, when internal pressure builds up the plug will be pushed away from its seat, providing an opening for the gasses to be relieved to the atmosphere. 15 An optical level indicator 81 is assembled to top cap 58 to allow observation when maximum liquid level is reached. This is extremely useful for the fill-up procedure. Optionally the reservoir 80 can be provided with a level sensing means to provide information on actual 20 level of electrolyte, or signalize that a predetermined minimum level has been reached. The electrolysis cell 50 is provided with an electrode assembly 10 mounted in a cartridge according to 25 the present invention. The cathode and anode electrode plates 16 and 18 are provided with adapters 70 for electrical connection to the positive and negative supply from the motor vehicle electrical system. When the electrode assembly is placed within the case 52, the 30 adapters 70 are aligned with openings 72 in the case 52 for connection of a terminal 74. The portion of the interior of the case 52 where the electrode assembly is located, provides the reservoir chamber for holding of the electrolyte solution and operation of the electrolysis. 35 The above of the reservoir chamber is provided a perforated spacer disc to separate the gas accumulation zone from the reservoir chamber. The gas accumulation chamber 70 is filled with a 40 multitude of balls 71 made of an inert material, preferably - 6 - WO00/00671 PCT/CA99/00590 polypropylene. The balls 71 play the role of a mechanical barrier for the gasses exiting the cell 50, removing airborne moisture particles and drying the gasses. Also they act as an anti-splash for the electrolyte and reduce 5 the volume of accumulated gasses limiting the negative repercussions in case of a secondary ignition inside the cell 50. The electrolyte solution utilized within the 10 electrolysis cell 10, is preferably a basic aqueous solution to provide for increased efficiency of the electrolysis reaction. Preferably, the solution is also adjusted to remain in solution form and not freeze at extremely low temperatures, down to -40 0 C or more. Most 15 preferably, the electrolyte solution is a 20 to 30% KOH solution. Although various preferred embodiments of the present invention have been described herein in detail, it 20 will be appreciated by those skilled in the art, that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims. - 7 -

Claims (6)

1. An assembly of monopolar electrodes for use in an electrical apparatus, the electrode assembly comprising a pair of electrodes, each of the electrodes being a plurality of spaced apart electrode plates connected together in series, the electrode plates of each of the electrodes being connected to the next electrode plate in the series by a bridging member contiguous with each of the interconnected electrode plates.

2. An electrode for use in an electrical assembly, the electrode comprising a plurality of electrode plates connected in series, each of the electrode plates being connected to the next plate in the series by a bridging strap contiguous with each of the interconnected electrode plates.

3. An electrochemical cell for production of gases by electrolysis the cell comprising an electrode assembly, a liquid reservoir and an internal gas dryer.

4. An electrochemical cell as claimed in claim 3, wherein the gas dryer comprises a mechanical barrier for removing airborne moisture, reducing the volume of accumulated gasses and reducing splashing of liquid.

5. An electrochemical cell as claimed in claim 4, wherein the internal liquid reservoir is provided with a means of sensing and monitoring liquid levels.

6. An electrochemical cell as claimed in any one of claim 3 to 5, wherein the electrode assembly comprises a pair of electrodes, each of the electrodes being a plurality of spaced apart electrode plates connected together in series, the electrode plates of each of the electrodes being connected to the next electrode plate in the series by a bridging member contiguous with each of the interconnected electrode plates. - 8 -