Solid Oxide Fuel Cells, Electrolyzers, and Sensors, and Methods of Making and Using the Same

Abstract

The present invention provides solid oxide fuel cells, solid oxide electrolyzer cells, solid oxide sensors, components of any of the foregoing, and methods of making and using the same. In some embodiments, a solid oxide fuel cell comprises an air electrode (or cathode), a fuel electrode (or anode), an electrolyte interposed between the air electrode and the fuel electrode, and at least one electrode-electrolyte transition layer. Other embodiments provide novel methods of producing nano-scale films and / or surface modifications comprising one or more metal oxides to form ultra-thin (yet fully-dense) electrolyte layers and electrode coatings. Such layers and coatings may provide greater ionic conductivity and increased operating efficiency, which may lead to lower manufacturing costs, less-expensive materials, lower operating temperatures, smaller-sized fuel cells, electrolyzer cells, and sensors, and a greater number of applications.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims benefit of priority under 35 U.S.C. §120 and is a continuation of U.S. Non-Provisional patent application Ser. No. 14 / 093,445, filed on Nov. 30, 2013 and entitled, “Solid Oxide Fuel Cells, Electrolyzers, and Sensors, and Methods of Making and Using the Same,” now allowed; which claims benefit of and is a continuation of U.S. Non-Provisional patent application Ser. No. 12 / 420,457, filed on Apr. 8, 2009, now U.S. Pat. No. 8,623,301 B1, entitled, “Solid Oxide Fuel Cells, Electrolyzers, and Sensors, and Methods of Making and Using the Same;” which claims benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61 / 043,566 filed on Apr. 9, 2008, and entitled, “Solid Oxide Fuel Cells, Electrolyzers, and Sensors, and Methods of Making and Using the Same.” Each of the foregoing applications is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates ...

AI Technical Summary

Benefits of technology

[0008]In view of the foregoing problems and disadvantages associated with the high operating temperatures of solid oxide cells, it would be desirable to provide solid oxide cells that can demonstrate lower operating temperatures. In addition, providing solid oxide cells and components that better tolerate higher temperatures would be advantageous. Moreover, the efficiency losses due to the thickness of electrolytes make thinner electrolytes desirable.

[0009]As used herein, “solid oxide cell” means any electrochemical cell that contains at least one metal oxide, and refers to, for example, solid oxide fuel cells, solid oxide electrolyzer cells, cells that can operate as a fuel cell and an electrolyzer cell, and solid oxide sensors. One method of lowering operating temperatures of solid oxide cells is to increase the efficiency of oxygen transport across the solid electrolyte. Since oxygen transport efficiency decreases linearly with electrolyte thickness, the thinner the electrolyte layer, the higher the efficiency of oxygen transport. Thus, the thinner the electrolyte, the higher the operating efficiency of the solid oxide cell will be. A thinner electrolyte layer also can lower the operating temperature of a solid oxide cell.

Problems solved by technology

The need for exotic materials greatly increases the costs of solid oxide fuel cells, making their use in certain applications cost-prohibitive.

Moreover, high operating temperatures often induce grain growth in the various component layers of a solid oxide fuel cell, including the electrolyte.

Differences in coefficients of thermal expansion between component layers of a solid oxide fuel cell can lead to cracking at interfaces of the layers as well as within the layers.

Differences in coefficients of thermal expansion between the air electrode and the electrolyte, for example, can lead to cracking at the electrode-electrolyte interface and within the electrode and / or electrolyte.

In conventional electrolyzers, electrical energy is lost in the electrolysis reaction driving the diffusion of ions through the electrolyte and across the distance between the electrodes.

However, at higher temperatures, electrolyzers face similar thermal stresses and cracking caused by differences in coefficients of thermal expansion between component layers of the solid oxide electrolyzer cell.

Moreover, given the high operating temperature of lambda sensors and similar devices, sensors face thermal stresses, cracking, and delamination issues similar to those facing fuel cells and electrolyzers.

Moreover, the efficiency losses due to the thickness of electrolytes make thinner electrolytes desirable.

In addition, by lowering the operating temperature of a solid oxide cell, less exotic and easier-to-fabricate materials can be utilized in the construction of the cell leading to lower production costs.

Incorporating higher porosity levels in ceramic materials renders them too structurally weak to support cell construction.

High sintering temperatures during fabrication of various components, such as the electrolyte, can result in excessive grain growth as well as compound problems associated with variances in coefficients of thermal expansion.

Furthermore, sintering provides little control over the ability to vary the composition of an electrolyte or electrode as a function of the thickness of the electrolyte or electrode.

If the electrode is too thin, then it may be too brittle.

If it is too thick, movement of gas through the electrode may hinder cell operation.

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