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EP-4406037-B1 - ELECTROCHEMICAL CELL UNIT WITH IMPROVED SEPARATOR PLATE

EP4406037B1EP 4406037 B1EP4406037 B1EP 4406037B1EP-4406037-B1

Inventors

  • NOBBS, Christopher James
  • GAWEL, Duncan Albert Wojciech
  • HERCZ, ZOLTAN

Dates

Publication Date
20260506
Application Date
20220921

Claims (15)

  1. An electrochemical cell unit (401) comprising: a cell layer (405) comprising an electrochemically active cell region (307); and, a separator plate (410) comprising a metal sheet overlying the cell layer; wherein the separator plate has a selectively shaped three dimensional (3D) region that overlies at least part of the electrochemically active cell region; and in that three dimensional (3D) region: the metal sheet has been deformed into a first plurality of outwardly extending dimpled protrusions (430, 433) that define the height of a first fluid volume on a first side of the separator plate; additionally, the metal sheet has been deformed into a second plurality of outwardly extending dimpled protrusions (435, 438) that define the height of a second fluid volume on a second side of the separator plate; whereby a mid-plane region (443) is disposed between the protrusions; and, the mid-plane region is so shaped as selectively to vary its height in at least one direction across the active cell region such that the interrelated respective heights of the first and second fluid volumes are correspondingly increased and decreased as a result.
  2. The electrochemical cell unit claim 1, comprising an inlet (316, 716, 816) to and an outlet (316, 717, 817) from the first fluid volume positioned towards opposing edges of the cell unit with the electrochemically active cell region positioned therebetween, and wherein the at least one direction of height variation in the mid-plane region is such that the height of the first fluid volume is smaller in a central area of the cell unit than in an area adjacent to an edge of the cell unit.
  3. The electrochemical cell unit of claim 1 or 2, wherein the at least one direction of height variation in the mid-plane region is generally perpendicular to a straight line between an inlet to and an outlet from the first fluid volume, and wherein the height of the first fluid volume is smaller along the straight line than to at least one side of the straight line.
  4. The electrochemical cell unit of claim 1, comprising an inlet (316, 716, 816) to and an outlet (316, 717, 817) from the first fluid volume positioned towards opposing edges of the cell unit with the electrochemically active cell region positioned therebetween, and wherein the at least one direction of height variation in the mid-plane region is such that the height of the first fluid volume decreases from the inlet to the outlet of the first fluid volume.
  5. The electrochemical cell unit of claim 4, comprising an inlet (316, 716, 816) to and an outlet (316, 717, 817) from the second fluid volume positioned towards or outwith opposing edges of the cell unit with the electrochemically active cell region positioned therebetween, the inlet and outlet of the second fluid volume positioned such that the height of the second fluid volume increases from the inlet to the outlet of the second fluid volume.
  6. The electrochemical cell unit of claim 5, wherein the second fluid volume includes a bypass for second fluid around a portion of the 3D region proximal to the inlet to the second fluid volume.
  7. The electrochemical cell unit of any preceding claim, wherein the 3 dimensional (3D) region overlies all of the electrochemically active cell region (307).
  8. The electrochemical cell unit of any preceding claim, whereby the dimpled protrusions of the first and second plurality of dimpled protrusions are shaped such that their outermost portions do not comprise any laterally extending contact portions that extend heightwise the full height of a fluid volume so as to form a channel within that fluid volume within which flow is constrained.
  9. The electrochemical cell unit of any preceding claim, wherein the first side of the separator plate (410) faces the cell layer (405) and a contact portion of each of the first plurality of dimpled protrusions contact the cell layer.
  10. The electrochemical cell unit of claim 9, wherein the contact portion of each of the first plurality of dimples and a contact portion of each of the second plurality of dimples respectively form first and second planes, the first and second planes each being planar and parallel to one another.
  11. The electrochemical cell unit of any preceding claim, wherein the cell unit is a metal-supported cell unit such that the cell layer (405) comprises a metal support plate carrying, on a first side thereof, the electrochemically active cell region (307) provided over a porous region.
  12. The electrochemical cell unit of any preceding claim, wherein the first fluid volume is for fuel, and the second fluid volume is for oxidant.
  13. An electrochemical cell stack (400) comprising a plurality of electrochemical cell units (401) according to any one of the preceding claims, wherein: the first side of the separator plate (410) of a first electrochemical cell unit (401a) faces the cell layer (405) of the first electrochemical cell unit and encloses the first fluid volume therebetween, and the second side of the separator plate (410) of the first electrochemical cell unit (401a) faces a cell layer of a second, neighbouring, electrochemical cell unit (401b) in the stack of cell units and encloses the second fluid volume therebetween.
  14. The electrochemical cell stack of claim 13, further comprising means for supply and exhaust of first fluid from the first fluid volume, wherein the means for supply and exhaust of first fluid from the first fluid volume comprises at least one fluid port (316, 716, 816) provided through the separator plate and the cell layer which is in fluid communication with the first fluid volume, wherein the at least one fluid port of the respective cell units align to form at least one passageway extending in the stack direction, these being internally manifolded passageways.
  15. A method for manufacturing a separator plate, comprising providing a planar metal sheet; and deforming the metal sheet to provide a three dimensional (3D) region, the three dimensional (3D) region comprising: a first plurality of outwardly extending dimpled protrusions that define the height of a first fluid volume on a first side of the separator plate; a second plurality of outwardly extending dimpled protrusions that define the height of a second fluid volume on a second side of the separator plate; whereby a mid-plane region is disposed between the protrusions; and, the mid-plane region is so shaped as selectively to vary its height in at least one direction across the active cell region such that the interrelated respective heights of the first and second fluid volumes are correspondingly increased and decreased as a result.

Description

Field of the Invention The present invention relates to electrochemical cell units, in particular, fuel cell units and electrolyser cell units, stacks containing such cell units, methods for manufacturing a separator plate for use in such cell units, separator plates so formed, and the use of such cell units. The cell units of the present invention include cells of solid oxide, polymer electrolyte membrane, and molten carbonate types. The present invention more specifically relates to solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) units, and these may include metal-supported solid oxide fuel cell (MS-SOFC) or electrolyser cell (MS-SOEC) units. Background to the Invention Some fuel cell units can produce electricity by using an electrochemical conversion process that oxidises fuel to produce electricity. Some fuel cell units can also, or instead, operate as regenerative fuel cells (or reverse fuel cells) units, often known as electrolyser fuel cell units, for example to separate hydrogen and oxygen from water, or carbon monoxide and oxygen from carbon dioxide. They may be tubular or planar in configuration. Planar fuel cell units may be arranged overlying one another in a stack arrangement, for example 100-200 fuel cell units in a stack, with the individual fuel cell units arranged, for example, electrically in series. A solid oxide fuel cell (SOFC) unit that produces electricity is based upon a solid oxide electrolyte that conducts negative oxygen ions from a cathode to an anode located on opposite sides of the electrolyte. For this, a fuel, or reformed fuel, contacts the anode (fuel electrode) and an oxidant, such as air or an oxygen rich fluid, contacts the cathode (air electrode). Conventional ceramic-supported (e.g. anode-supported) SOFCs have low mechanical strength and are vulnerable to fracture. Hence, metal-supported SOFCs have been developed which have the active fuel cell component layer supported on a metal substrate. In these cells, the ceramic layers can be very thin since they only perform an electrochemical function: that is to say, the ceramic layers are not self-supporting but rather are thin coatings/films laid down on and supported by the metal substrate. Such metal supported SOFC stacks are more robust, lower cost, have better thermal properties than ceramic-supported SOFCs and can be manufactured using conventional metal welding techniques. A solid oxide electrolyser cell (SOEC) may have the same structure as an SOFC but is essentially that SOFC operating in reverse, or in a regenerative mode, to achieve the electrolysis of water and/or carbon dioxide by input of electrical energy and using the solid oxide electrolyte to produce hydrogen gas and/or carbon monoxide and oxygen. The present invention is directed at an electrochemical cell unit and concerns the design of their separator plates. It is thus applicable to various types of fuel and electrolyser cells, for example, based on solid oxide electrolytes, polymer electrolyte membranes, or molten electrolytes. For convenience, "cell units" is used to refer to "electrochemical cell units" including fuel or electrolyser cell units. Each cell unit in a stack of cell units typically includes a cell layer comprising an electrochemically active cell region (such as a metal-supported electrochemically active cell region) and a separator plate. A separator plate typically contacts one side of the cell layer of its cell unit and, in a stack of cell units, may also contact an opposite side of a cell layer of an adjacent cell unit. Fig. 1 is drawn from WO 2020/126486 A1. Fig. 1 shows an exploded view of a fuel cell unit 10, and two gaskets 34. The fuel cell unit 10 comprises a flat metal support plate 14 stacked next to a separator plate 12. The separator plate 12 is shown to have flanged perimeter features 18 around its perimeter. The flanged perimeter features 18 extend out of the predominant plane of the sheet, as found at a central fluid volume area, to form the fluid volume 20 within this fuel cell unit upon assembly of the fuel cell unit. In a middle portion of the fuel cell unit 10, an electrochemically active cell region 50 (i.e. comprising the electrochemically active layers) is provided on the metal support plate, located outside of the fluid volume 20. The metal support plate 14 is provided with multiple small holes (not shown) to enable fluid in the fluid volume 20 to be in contact with the side of the electrochemical layer that is closest to the metal support plate 14. The anode (fuel electrode) layer may be located adjacent the small holes with the fluid volume 20 within the fuel cell unit comprising a fuel flow volume 20 supplied by fuel entering and exiting via the fluid ports 22, which are thus fuel ports 22. The cathode (air electrode) layer may be on the opposite side of the electrochemically active cell region 50, i.e. on its outer face, and is exposed to air flowing across that layer during use of the f