MEMS-based thin-film fuel cells

Abstract

A micro-electro-mechanical systems (MEMS) based thin-film fuel cells for electrical power applications. The MEMS-based fuel cell may be of a solid oxide type (SOFC) having a thickness of 0.5-50 μm at a temperature below 600° C. and a thickness of 0.5-7.5 μm at a temperature over 600° C., or a solid polymer type (SPFC), or a proton exchange membrane type (PEMFC), each operating below 600° C. and having a thickness of 0.5-50 μm, and each fuel cell basically consists of an anode and a cathode separated by an electrolyte layer. The electrolyte layer can consist of either a solid oxide or solid polymer material, or proton exchange membrane electrolyte materials may be used. Additionally catalyst layers can also separate the electrodes (cathode and anode) from the electrolyte. Gas manifolds are utilized to transport the fuel and oxidant to each cell and provide a path for exhaust gases. The electrical current generated from each cell is drawn away with an interconnect and support structure integrated with the gas manifold. The fuel cells utilize integrated resistive heaters for efficient heating of the materials. By combining MEMS technology with thin-film deposition technology, thin-film fuel cells having microflow channels and full-integrated circuitry can be produced that will lower the operating temperature an will yield an order of magnitude greater power density than the currently known fuel cells.

What is claimed is:  
     
         1 . A fuel cell, including: 
 a fuel cell stack having an electrolyte composed of material selected from the group consisting of solid oxide, solid polymer, and proton exchange membrane materials,    means for supplying fuel and an oxidant to opposite sides of said fuel cell stack, and means for heating said fuel cell stack,    said means for heating includes a resistive heater,    said fuel cell stack including at least a pair of electrodes, and an electrolyte separating said electrodes,    said electrolyte having a thickness of about 0.5-50 μm,    said means for supplying fuel and oxidant including at least one substrate having a manifold formed therein,    said manifold directing fuel to one side of said fuel cell stack.    
     
     
         2 . The fuel cell of  claim 1 , wherein said means for supplying fuel and oxidant additionally includes a second substrate having a manifold formed therein for directing an oxidant to an opposite side of said fuel cell stack.  
     
     
         3 . The fuel cell of  claim 1 , wherein said fuel cell stack includes a catalyst adjacent the electrolyte.  
     
     
         4 . The fuel cell of  claim 1 , wherein said resistive heater is located in said fuel cell stack.  
     
     
         5 . The fuel cell of  claim 1 , wherein said pair of electrodes of said fuel cell stack includes a first electrode composed of hydrogen catalyzing conducting material selected from nickel, copper, carbon, platinum, and palladium, and a second electrode composed of oxygen catalyzing conducting material selected from silver, carbon, platinum, lanthanum strontium manganate (LSM).  
     
     
         6 . The fuel cell of  claim 1 , wherein said pair of electrodes comprises a first electrode composed of Ni, and a second electrode composed of Ag and wherein said electrolyte is composed of YSZ.  
     
     
         7 . The fuel cell of  claim 1 , wherein said at least one substrate is composed of material selected from the group consisting of silicon, glass, ceramic, and plastic.  
     
     
         8 . The fuel cell of  claim 1 , wherein said means for supplying fuel includes a second substrate bonded to said at least one substrate, said second substrate having at least a fuel inlet extending thereinto and in open communication with said manifold in said at least one substrate.  
     
     
         9 . The fuel cell of  claim 8 , wherein said second substrate additionally includes a cutaway section in a surface located adjacent said at least one substrate and which is in open communication with said manifold and with said fuel inlet.  
     
     
         10 . The fuel cell of  claim 8 , wherein said second substrate additionally includes a plurality of channels in open communication with said manifold and said fuel inlet.  
     
     
         11 . The fuel cell of  claim 1 , additionally including a porous member located intermediate said fuel cell stack and said manifold in said at least one substrate.  
     
     
         12 . The fuel cell of  claim 1 , wherein said manifold of said at least one substrate is composed a plurality of channels.  
     
     
         13 . The fuel cell of  claim 12 , wherein said means for supplying fuel includes a second substrate bonded to said at least one substrate, said second substrate having a fuel inlet and a plurality of channels in open communication with said manifold in said at least one substrate.  
     
     
         14 . The fuel cell of  claim 1 , wherein said electrolyte is composed of solid polymer or proton exchange membrane material, operating at a temperature range of about 23-120° C., and having a thickness in the range of 0.5-50 μm.  
     
     
         15 . The fuel cell of  claim 1 , wherein said electrolyte is composed of solid oxide materials operating at one of a temperature below 600° C. with a thickness of 0.5-7.5 μm or 0.5-50 μm, or at a temperature above 600° C. with a thickness of 0.5-7.5 μm.  
     
     
         16 . A miniature thin-film fuel cell, comprising: 
 a fuel cell stack including a pair of electrodes and an electrolyte layer, selected from the group consisting of solid oxides, solid polymers, and proton exchange membrane materials,    a resistive heater for heating said fuel cell stack,    a first substrate having an opening therein located adjacent said fuel cell stack,    a second substrate having at least a fuel inlet therein secured to said first substrate and,    a resistive heating means located in said fuel cell stack for at least said electrolyte,    said electrolyte having a thickness of 0.5 to 50 μm.    
     
     
         17 . The fuel cell of  claim 16 , additionally including a third substrate secured to said first substrate and having an oxidant inlet and a manifold therein adjacent said fuel cell stack.  
     
     
         18 . The fuel cell of  claim 16 , wherein said first substrate additionally includes a plurality of channels forming said opening.  
     
     
         19 . The fuel cell of  claim 18 , wherein said second substrate additionally includes a plurality of channels in open communication with said fuel inlet and said plurality of channels in said first substrate.  
     
     
         20 . The fuel cell of  claim 16 , additionally including a porous member intermediate said first substrate and said fuel cell stack.  
     
     
         21 . The fuel cell of  claim 1 , additionally including a porous electrode formed by photolithographically patterning and etching a continuous metal electrode layer.  
     
     
         22 . The fuel cell of  claim 16 , additionally including a porous electrode formed by photolithographically patterning and etching a continuous metal electrode layer.  
     
     
         23 . The fuel cell of  claim 16 , additionally including a porous electrode formed by deposition onto a porous member.  
     
     
         24 . The fuel cell of  claim 21 , additionally including a catalyst and electrolyte layers deposited onto a porous electrode structure.  
     
     
         25 . The fuel cell of  claim 22 , additionally including a catalyst and electrolyte layers deposited onto a porous electrode structure.  
     
     
         26 . The fuel cell of  claim 1 , in which a membrane electrode assembly laminate structure is attached, bonded or mechanically sealed to a micromachined manifold host structure.  
     
     
         27 . The fuel cell of  claim 16 , in which a membrane electrode assembly laminate structure is attached, bonded or mechanically sealed to a micromachined manifold host structure.  
     
     
         28 . The fuel cell of  claim 17 , in which the fuel cell modules can be directly stacked on top of each other to scale voltage and power.  
     
     
         29 . The fuel cell of  claim 28 , additionally including a plurality of fuel inlets to deliver fuel from a common reservoir.  
     
     
         30 . The fuel cell of  claim 16 , wherein said electrolyte is composed of solid polymer material or proton exchange membrane material having a thickness of 0.5-50 μm, and wherein said fuel cell operates at a temperature below 600° C.  
     
     
         31 . The fuel cell of  claim 30 , wherein said operating temperature is about 23°-120° C.  
     
     
         32 . The fuel cell of  claim 16 , wherein said electrolyte is a solid oxide material having a thickness of 0.5-50 μm, and wherein said fuel cell operates at a temperature above 600° C. and below 600° C.  
     
     
         33 . The fuel cell of  claim 32 , wherein the operating temperature is below 600° C., and wherein said electrolyte has a thickness of 0.5-50 μm.  
     
     
         34 . The fuel cell of  claim 33 , wherein the electrolyte has a thickness of less than 10 μm.  
     
     
         35 . The fuel cell of  claim 34 , wherein the electrolye has a thickness of 0.5-7.5 μm.  
     
     
         36 . The fuel cell of  claim 32 , wherein said electrolyte has a thickness of about 0.5-7.5 μm, and wherein the operating temperature is above 600° C.  
     
     
         37 . The fuel cell of  claim 36 , wherein said operating temperature is 675° C.