Heavily-Doped Ceria Composite Electrode for Stable High-Temperature Cells
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Solution Overview
Problem
Existing electrode materials for high-temperature solid oxide fuel and electrolyzer cells face challenges such as reactivity with common electrolytes, high thermal expansion coefficients, and reduced mechanical stability, which affect performance and stability at operating temperatures above 700°C.
Innovation Solution
A composite electrode material comprising a heavily-doped ceria phase and an Ln2MO4 phase, where the dopant concentration is at least 40 mol%, reducing reactivity and thermal expansion, and maintaining stability and porosity, thereby enhancing electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high operating temperatures (>700°C) are used, then reaction kinetics and ionic membrane resistance are improved, but electrode performance deteriorates
Solution Approach 1:
The patent employs a composite electrode structure consisting of a ceria-based layer (with or without perovskite) combined with specific material compositions that maintain stability at high temperatures. The ceria-based material with controlled dopant content (0.01-0.20 oxygen vacancies per formula unit) provides both high-temperature stability and sustained electrochemical performance, resolving the contradiction between operating temperature and electrode performance.
Solution Approach 2:
The patent optimizes the oxygen vacancy concentration parameter in the ceria-based material to a specific range (0.01-0.20 per formula unit). This parameter control allows the material to maintain appropriate ionic conductivity and structural stability at high temperatures without suffering from excessive thermal expansion or degradation, thus preserving electrode performance at elevated operating temperatures.
2Quantity of substance
If ceria volume percentage is increased, then electrode performance is improved, but reactivity with electrolyte increases
Solution Approach 1:
The patent applies local quality control by restricting ceria to specific layers (first and/or second layers) of the electrode structure, rather than uniformly distributing it throughout. The ceria-based material is positioned in layers where it provides performance benefits, while other layers (such as the third layer) use different materials that are less reactive with the electrolyte, thus allowing high ceria content where needed while minimizing overall reactivity issues.
Solution Approach 2:
The patent introduces a perovskite phase as an intermediary component in certain embodiments, where the perovskite layer acts as a buffer between the ceria-based material and the electrolyte. This intermediary layer reduces direct contact and chemical interaction between reactive ceria and the electrolyte, allowing higher ceria volume percentages to be used without proportionally increasing reactivity problems.
3Use of energy by moving object
If dopant concentration in ceria is increased, then ionic conductivity is improved, but thermal expansion coefficient increases
Solution Approach 1:
The patent precisely controls the dopant concentration parameter in ceria, limiting oxygen vacancies to 0.01-0.20 per formula unit. This optimized parameter range ensures sufficient ionic conductivity for high-temperature operation while preventing excessive thermal expansion that would occur at higher dopant levels. The balanced composition achieves both improved ionic conductivity and acceptable thermal stability.
Solution Approach 2:
The patent applies different dopant concentrations to different layers of the electrode structure. The ceria-based material in specific layers contains controlled amounts of dopants to provide necessary ionic conductivity, while other layers use undoped or lightly-doped materials to maintain low thermal expansion coefficients. This layered approach with varying local compositions resolves the contradiction between ionic conductivity and thermal expansion.
Data Source
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AI summary
An electrode can include a functional layer having an Ln2MO4 phase, where Ln is at least one lanthanide optionally doped with a metal and M is at least one 3d transition metal, and a heavily-doped ceria phase. An electrochemical device or a sensor device can include the electrode.