Solid Oxide Fuel Cell Forsterite Support CaO Control
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Solution Overview
Problem
Solid oxide fuel cells using forsterite and lanthanum-gallate-based oxide materials fail to generate electrical power due to the diffusion of Ca from the forsterite support material, which forms a diffusion layer and disrupts the crystal structure of the lanthanum-gallate-based oxide electrolyte during firing.
Innovation Solution
Reducing the CaO content in the forsterite porous support to 0.2 mass % or less, and using lanthanum-gallate-based oxide doped with Sr and Mg as the solid electrolyte, maintains the crystal structure and prevents the formation of a diffusion layer, ensuring high power generation performance at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If forsterite-based sintered compact is used as a porous support material to reduce cost, then manufacturing cost is reduced, but Ca diffuses out during firing forming a diffusion layer that prevents power generation
Solution Approach 1:
The patent applies parameter changes by controlling the CaO content in the forsterite-based porous support to be 0.03 mass% or less. This specific parameter control prevents excessive Ca diffusion during firing while maintaining the cost advantage of forsterite-based materials over NiO-YSZ. The low CaO content ensures the solid electrolyte layer maintains its crystal structure and enables power generation.
Solution Approach 2:
The patent applies local quality by ensuring the porous support material has uniformly low CaO content (0.03 mass% or less) throughout its composition. This localized control of Ca content in the support material prevents formation of Ca-containing diffusion layers at the interface with the solid electrolyte, while allowing the rest of the fuel cell structure to use cost-effective forsterite-based materials.
2Temperature
If lanthanum-gallate-based oxide is used as solid electrolyte to enable low temperature operation, then operating temperature is reduced, but crystal structure is disrupted by Ca diffusion from forsterite support
Solution Approach 1:
The patent applies preliminary anti-action by pre-controlling the CaO content in the forsterite-based porous support to be 0.03 mass% or less before assembly. This preliminary control prevents Ca diffusion that would otherwise disrupt the lanthanum-gallate-based oxide crystal structure during low-temperature firing and operation, thereby maintaining electrolyte stability.
3Productivity
If Sr is doped in lanthanum-gallate-based oxide to enhance performance, then power generation performance is improved, but Sr is separated by Ca from the porous support forming diffusion layer
Solution Approach 1:
The patent applies the taking out principle by removing the harmful CaO impurity from the forsterite-based porous support material, reducing its content to 0.03 mass% or less. This extraction of the harmful element (Ca) prevents it from separating Sr from the solid electrolyte layer, thereby preventing diffusion layer formation and maintaining 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
Prevents the formation of a diffusion layer containing Ca, maintains the electrolyte's crystal structure, and achieves excellent power generation performance at low temperatures, making the fuel cell more efficient and cost-effective.
Implementation Method 1
Ca contained in the porous support is moved out of the porous support by firing, and combines with other elements moved from other layers, thereby forming a diffusion layer between the porous support and the inner electrode
Implementation Method 2
it is possible to maintain the crystal structure of the solid electrolyte layer even after the firing
Data Source
AI summary
An object of the present invention is to provide a fuel cell preventing formation of a diffusion layer containing Ca and other elements, and having an excellent power generation performance at low temperature by preventing breakdown of a crystal structure of an electrolyte by firing. Disclosed is a solid oxide fuel cell which includes an inner electrode, a solid electrolyte, and an outer electrode, each sequentially laminated on the surface of a porous support. The porous support contains forsterite, and has a Ca element content of 0.2 mass % or less in terms of CaO in a surface region at the inner electrode side.