Multilayer electrochemical cell technology using sol-gel processing applied to ceramic oxygen generator

Abstract

An electrochemical cell that receives an inlet stream of air and produces an outlet stream of a high oxygen concentration of gas. The cell is made up of a plurality of layers and preferably a porous electrolyte comprised of yttria stabilized zirconia (YSZ) that allows only oxygen ions to pass therethrough and which is covered on its sides with electrodes comprised of lanthanum strontium manganate (LSM) which in turn are coated with a layer of platinum to aid in the even distribution of the electrical current. An electrical current is passed through the electrodes to produce a voltage difference therebetween. The layers of YSZ and LSM are formed by a sol-gel process.

I claim: 
     
         1 . An electrochemical oxygen cell for producing a gas having a high oxygen concentration, said electrochemical oxygen cell comprising a substrate, an anodic electrode layer of lanthanum strontium manganate covering said substrate, an electrolyte layer comprised of yttria stabilized zirconia covering said anodic electrode layer, and a cathodic electrode layer of lanthanum strontium manganate covering said electrolyte layer, said electrochemical cell having an inlet for air to enter said electrochemical oxygen cell through said cathodic electrode layer and an outlet for the high oxygen concentration gas to emerge from said electrochemical cell from said anodic electrode, said anodic electrode layer and said cathodic electrode layer adapted to be connected to a source of electrical energy to cause the flow of air through said electrochemical cell. 
     
     
         2 . An electrochemical oxygen cell as defined in  claim 1  wherein said cathodic and anodic electrodes are about 20 microns in thickness. 
     
     
         3 . An electrochemical oxygen cell as defined in  claim 1  wherein said lanthanum strontium manganate layers are applied by the sol-gel process. 
     
     
         4 . An electrochemical oxygen cell as defined in  claim 1  wherein said substrate is an alumina ceramic material. 
     
     
         5 . An oxygen generator for producing a gas having a high oxygen concentration, said oxygen generator comprising a substrate, a first platinum layer covering a surface of said substrate, an anodic electrode of LSM covering said first platinum layer, an electrolyte comprised of YSZ covering said first platinum layer, a cathodic layer of LSM covering said electrolyte and a second platinum layer covering said cathodic layer, an inlet for air to enter said oxygen generator through said second platinum layer and an outlet for an enriched oxygen gas to emerge from said electrochemical cell for said first platinum layer, wherein said first and second platinum layers are adapted to be connected to a source of electrical energy to cause the flow of air through said electrochemical cell. 
     
     
         6 . An oxygen generator as defined in  claim 5  where said first and second platinum layers comprise a thinned platinum paste applied in a plurality of coats. 
     
     
         7 . An oxygen generator as defined in  claim 6  wherein certain of said coats are heat treated. 
     
     
         8 . A method of fabricating an electrochemical oxygen generator comprising the steps of:
 a) providing a substrate of a generally porous material,   b) coating a first electrode of lanthanum strontium manganate onto said substrate,   c) coating a solid electrolyte material of yttria stabilized zirconia onto the first electrode, and   d) coating a second electrode of lanthanum strontium manganate onto the solid electrolyte.   
     
     
         9 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein said step of coating a first electrode comprises using a sol-gel process. 
     
     
         10 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein said step of coating a solid electrolyte material on to the first electrode comprises using a sol-gel process. 
     
     
         11 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein said step of coating a second electrode onto the solid electrolyte comprises using a sol-gel process. 
     
     
         12 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein said step of coating a solid electrolyte of yttria stabilized zirconia comprises preparing a gel of a mixture of zirconia olylchloride and yttria and coating the first electrode with a multiple layers of the prepared gel. 
     
     
         13 . A method of fabricating an electrochemical oxygen generator as defined in  claim 12  wherein the yttira is provided to the mixture in the form of Y(NO 3 ) 3 . 
     
     
         14 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein said step of coating a first electrode of lanthanum strontium manganate onto said substrate comprises preparing the lanthanum strontium manganate in the form of a gel and applying that gel to the substrate in a plurality of coats. 
     
     
         15 . A method of fabricating an electrochemical oxygen generator as defined in  claim 14  wherein said step of the step of preparing the gel comprises preparing a mixture comprising strontium nitrate, manganese acetate and lanthanum chloride. 
     
     
         16 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein    
     
     
         17 . A method of fabricating an electrochemical oxygen generator as defined in  claim 8  wherein steps b)-d) all comprises using a sol gel process to form said layers in a plurality of coatings and wherein said coatings are periodically, at predetermined intervals, subjected to a heat treatment. 
     
     
         18 . A method of fabricating an electrochemical oxygen generator comprising the steps of:
 a) providing a substrate of a generally porous material,   b) coating a platinum layer onto said substrate,   c) coating a first electrode of lanthanum strontium manganate onto said platinum layer,   d) coating a solid electrolyte material of yttria stabilized zirconia onto the first electrode,   e) coating a second electrode of lanthanum strontium manganate onto the solid electrolyte and   f) coating a platinum layer onto said second electrode.   
     
     
         19 . A method of fabricating an electrochemical oxygen generator as defined in  claim 18  wherein said steps b) and f) comprise using a thinned platinum paste and coating the thinned platinum paste by applying a plurality of coats of the thinned platinum paste. 
     
     
         20 . A method of fabricating an electrochemical oxygen generator as defined in  claim 18  wherein said steps of c) d) and e) comprise using a sol gel process by applying a plurality of coats. 
     
     
         21 . A method of fabricating an electrochemical oxygen generator as defined in  claim 20  wherein said applying a plurality of coats comprises brushing on each of the individual coats and applying a heat treatment after each predetermined number of coats. 
     
     
         22 . A method of fabricating an electrochemical oxygen generator as defined in  claim 21  wherein said step of applying a plurality of coats comprise heat treating the coats after every five coats by heating the coats to about 1100 degrees C. for a predetermined period of time.