Fuel Cell Intermediate Layer Suppressing Sr-Zr Diffusion
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Solution Overview
Problem
Fuel cells experience deteriorated power generation performance over time due to diffusion of Sr from the air electrode layer into the solid electrolyte layer and Zr from the solid electrolyte layer into the air electrode layer, leading to the formation of high-resistance reaction products, especially at low temperatures.
Innovation Solution
Incorporating two intermediate layers of CeO2 solid solution with rare-earth elements excluding Ce between the solid electrolyte layer and the air electrode layer, with controlled rare-earth element content to suppress diffusion and maintain ionic conductivity, and optimizing the composition and structure of the conductive support substrate, fuel electrode layer, and air electrode layer to enhance power generation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two intermediate layers of CeO2 solid solution containing rare-earth element excluding Ce are disposed between the solid electrolyte layer and the air electrode layer to suppress diffusion of Sr and Zr, then the formation of high-resistance reaction products is suppressed and long-term reliability is improved, but ionic conductivity in low temperature range (550°C to 650°C) around the interface is lowered when large amount of rare-earth element excluding Ce is present
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration of rare-earth element excluding Ce in the intermediate layer and the ratio of rare-earth element to Zr in the solid electrolyte layer. By adjusting these compositional parameters within specific ranges, the patent achieves optimal balance between suppressing diffusion (improving reliability) and maintaining ionic conductivity (preserving power generation performance at low temperatures).
Solution Approach 2:
The patent applies local quality by creating distinct compositional zones: the intermediate layer has controlled rare-earth element content to prevent diffusion, while the solid electrolyte layer has optimized rare-earth element to Zr ratio to maintain ionic conductivity. This spatial variation in material composition allows different regions to perform their specific functions optimally without compromising overall system performance.
2Reliability
If intermediate layer contains large amount of rare-earth element excluding Ce to effectively suppress diffusion, then reliability is improved, but ionic conductivity around the interface is lowered causing reduced power generation performance
Solution Approach 1:
The patent resolves this contradiction by changing the quantitative parameters of rare-earth element content. Specifically, it limits the rare-earth element excluding Ce content in the intermediate layer and controls the rare-earth element to Zr ratio in the solid electrolyte layer to be within specific ranges, thereby achieving optimal balance between diffusion suppression and ionic conductivity maintenance.
Solution Approach 2:
The patent applies partial action by using a moderate amount of rare-earth element excluding Ce in the intermediate layer rather than large amounts. This controlled, partial incorporation is sufficient to suppress diffusion while avoiding the excessive rare-earth element content that would harm ionic conductivity and power generation performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses the formation of high-resistance reaction products, improving power generation performance at low temperatures by maintaining ionic conductivity and reducing the diffusion of Sr and Zr, thereby enhancing the long-term reliability of fuel cells.
Implementation Method 1
since Sr contained in the air electrode layer diffuses into the solid electrolyte layer or Zr contained in the solid electrolyte layer diffuses into the air electrode layer in the course of manufacturing the fuel cells or generating electric power
Implementation Method 2
a solid electrolyte layer containing Zr; a value obtained by dividing a content of the rare-earth element excluding Ce by a content of Zr is equal to or less than 0.05 at a site of the solid electrolyte layer, the site being 1 μm away from an interface between the solid electrolyte layer and the intermediate layer
Data Source
AI summary
A fuel cell includes a solid electrolyte layer containing Zr; an intermediate layer containing CeO2 solid solution having a rare-earth element excluding Ce; an air electrode layer containing Sr, the intermediate layer and the air electrode layer being stacked in this order on one surface of the solid electrolyte layer; and a fuel electrode layer on another surface of the solid electrolyte layer which is opposite to the one surface. A value obtained by dividing a content of the rare-earth element excluding Ce by a content of Zr is equal to or less than 0.05 at a site of the solid electrolyte layer, the site being 1 μm away from an interface between the solid electrolyte layer and the intermediate layer.