Flow structures for use with an electrochemical cell
The design and method of fabrication of a three-dimensional, porous flow structure for use in a high differential pressure electrochemical cell is described. The flow structure is formed by compacting a highly porous metallic substrate and laminating at least one micro-porous material layer onto the compacted substrate. The flow structure provides void volume greater than about 55% and yield strength greater than about 12,000 psi. In one embodiment, the flow structure comprises a porosity gradient towards the electrolyte membrane, which helps in redistributing mechanical load from the electrolyte membrane throughout the structural elements of the open, porous flow structure, while simultaneously maintaining sufficient fluid permeability and electrical conductivity through the flow structure.
1. A flow structure for use in an electrochemical cell, comprising:
a compacted porous metallic substrate having a void volume greater than about 55% and yield strength greater than about 12,000 psi, wherein the compacted porous metallic substrate is formed by:
selecting a porous metallic substrate with a void volume between about 75% and about 98%; and
compacting uniformly the porous metallic substrate causing plastic deformation and thereby forming the compacted porous metallic substrate and increasing the yield strength to greater than about 12,000 psi;
at least one micro-porous material layer laminated on one side of the compacted porous metallic substrate, wherein an average pore size of the at least one micro-porous material layer is smaller than an average pore size of the compacted porous metallic substrate.
2. The flow structure of claim 1 , wherein a porosity gradient is formed through the flow structure by laminating a plurality of micro-porous material layers on the compacted porous metallic substrate, each micro-porous material layer having a pore size smaller than an immediately preceding layer.
3. The flow structure of claim 1 , wherein pore size of the at least one micro-porous material layer ranges from about 0.5 μm to about 10 μm.
4. The flow structure of claim 1 , wherein the compacted porous metallic substrate comprises a high density region and a low density region, wherein the high density region has lower porosity that the low density region.
5. The flow structure of claim 4 , wherein the high density region has a higher yield strength than the low density region.
6. The flow structure of claim 1 , further comprising one or more fillers laminated to a surface of the compacted porous metallic substrate after compaction, wherein the fillers make the surface substantially smooth and uniform.
7. The flow structure of claim 6 , wherein the surface has a surface flatness of less than about 0.0005 inches.
8. The flow structure of claim 6 , wherein the fillers form a covering on the surface having a thickness between about 0.01 inches to about 0.001 inches.
9. The flow structure of claim 6 , wherein the fillers are formed of at least one of graphite epoxy, carbon black, carbon fibers, graphite beads, or glass beads.
10. The flow structure of claim 6 , wherein the fillers include a binder configured to increase the strength of the fillers.
11. The flow structure of claim 10 , wherein the fillers include additives and the additives include at least one of pore formers, fibers, or powders.
12. An electrochemical cell for use in high differential pressure operations, comprising:
a first electrode, a second electrode, and a proton exchange membrane disposed therebetween;
a first flow structure in fluid and electrical communication with the first electrode, comprising:
a first compacted porous metallic substrate having a void volume greater than about 55% and yield strength greater than about 12,000 psi, wherein the first compacted porous metallic substrate is formed by:
selecting a porous metallic substrate with a void volume between about 75% and about 98%; and
compacting uniformly the porous metallic substrate causing plastic deformation and thereby forming the first compacted porous metallic substrate and increasing the yield strength to greater than about 12,000 psi;
at least one micro-porous material layer laminated on one side of the compacted porous metallic substrate, wherein an average pore size of the at least one micro-porous material layer is smaller than an average pore size of the compacted porous metallic substrate; and
a second flow structure comprising a second porous metallic substrate, wherein the second flow structure is in fluid and electrical communication with the second electrode.
13. The electrochemical cell of claim 12 , wherein at least one of the first and the second flow structures comprise a porosity gradient along the flow structure.
14. The electrochemical cell of claim 12 , wherein the first flow structure is compacted to a density level greater than that of the second flow structure.