Fuel Cell Cathode Strontium Sulfate Gradient Crack Resistance
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Solution Overview
Problem
Micro-cracks can form near the surface of the cathode in fuel cells when temperature changes, potentially leading to cracks that affect the cathode's performance over long-term operation, necessitating a solution to inhibit their formation.
Innovation Solution
The fuel cell design includes a cathode with a surface region and an inner region, both containing perovskite oxide, where the surface region has a higher occupied surface area ratio of strontium sulfate than the inner region, enhancing the porous structure's strength and preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode is subjected to high temperature firing or repeated temperature changes during operation, then the cathode achieves proper sintering and electrical characteristics, but micro-cracks form near the surface of the cathode
Solution Approach 1:
The invention applies local quality by creating a surface region with different composition and properties from the inner region. The surface region contains a higher proportion of strontium sulfate secondary phase, which provides crack resistance specifically where needed (at the surface exposed to temperature changes), while the inner region maintains the perovskite oxide composition for electrical functionality. This localized modification resolves the contradiction by strengthening the surface without compromising the bulk cathode properties.
Solution Approach 2:
The invention uses composite materials by combining perovskite oxide (main phase) with strontium sulfate (secondary phase) in a spatially varying ratio. The surface region has a composite structure with more strontium sulfate (5-20 wt%), while the inner region has less (0.1-5 wt%). This composite approach allows the surface to resist thermal stress and crack formation while the inner region maintains good electrical characteristics for fuel cell operation.
2Strength
If the cathode surface is strengthened to prevent micro-crack formation, then crack resistance improves, but the cathode's electrical performance may be compromised
Solution Approach 1:
The invention resolves this contradiction by applying local quality - the surface region (within 5 μm from the surface) contains more strontium sulfate for crack resistance, while the inner region maintains higher perovskite oxide content for electrical performance. This spatial differentiation ensures that each region optimizes for its specific function without compromising the other.
Solution Approach 2:
The invention applies parameter changes by varying the composition parameter (strontium sulfate content) across the cathode thickness. The surface region has 5-20 wt% strontium sulfate while the inner region has 0.1-5 wt%, creating a gradient that transitions from crack-resistant surface to electrically active interior. This parameter variation allows simultaneous optimization of both crack resistance and electrical characteristics.
Data Source
AI summary
The fuel cell has an anode, a cathode, and a solid electrolyte layer. The cathode contains a main component containing a perovskite oxide of the general formula ABO3 and includes at least Sr at the A site. The solid electrolyte layer is disposed between the anode and the cathode. The cathode has a surface region and an inner region. The surface region is within 5 μm from a surface opposite the solid electrolyte layer. The inner region is formed on a solid electrolyte layer side of the surface region. The surface region and the inner region respectively include a main phase containing the perovskite oxide and a secondary phase containing strontium sulfate. An occupied surface area ratio of the secondary phase in a cross section of the surface region is greater than an occupied surface area ratio of the secondary phase in a cross section of the inner region.