Low Temperature Electrolytes for Solid Oxide Cells Having High Ionic Conductivity

Abstract

Some embodiments of the present invention provide solid oxide cells and components thereof having a metal oxide electrolyte that exhibits enhanced ionic conductivity. Certain of those embodiments have two materials, at least one of which is a metal oxide, disposed so that at least some interfaces between the domains of the materials orient in a direction substantially parallel to the desired ionic conductivity.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application claims benefit of priority under PCT Article 8 and 35 U.S.C. §119(e) of U.S. Provisional Application No. 61 / 303,003, filed on Feb. 10, 2010, entitled, “LOW TEMPERATURE ELECTROLYTES FOR SOLID OXIDE CELLS HAVING HIGH IONIC CONDUCTIVITY.” That provisional application is incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT[0002]This invention was made with government support awarded by the Department of Energy and administered by Oak Ridge National Laboratory / UT Battelle. The government has certain rights in the invention.FIELD OF THE INVENTION[0003]The present invention relates to electrical energy systems such as fuel cells, electrolyzer cells, and sensors, and, in particular, to solid oxide fuel cells, solid oxide electrolyzer cells, solid oxide sensors, and components of any of the foregoing.BACKGROUND OF THE INVENTION[0004]Solid oxide fuel cells, otherwi...

AI Technical Summary

Benefits of technology

The present invention provides a method to enhance the conductivity of ionic metal oxides in solid oxide cells, which allows for lower operating temperatures. This results in the use of simpler and less expensive materials in the construction of the cells, leading to lower production costs. The lower operating temperatures also allow for higher strength in metal components, allowing for higher levels of porosity. Additionally, the invention reduces degradation processes associated with variances in coefficients of thermal expansion between components of the cell. Finally, the invention produces a desirable surface catalytic effect, resulting in more chemically active sites at triple phase boundaries for more efficient fuel cell operation.

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.

Significantly, the high operating temperature is required because of poor low temperature ion conductivity.

However, high proton conductivity requires precise control of hydration in the electrolyte.

If the electrolyte becomes too dry, proton conductivity and cell voltage drop.

If the electrolyte becomes too wet, the cell becomes flooded.

Electro-osmotic drag complicates hydration control: protons migrating across the electrolyte “drag” water molecules along, potentially causing dramatic differences in hydration across the electrolyte that inhibit cell operation.

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 components 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.

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 compound problems associated with variances in coefficients of thermal expansion.

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