Solid Oxide Fuel Cell Interconnector Joining with Dense Conductive Ceramics
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Solution Overview
Problem
The connection strength and reliability of electric connections in solid oxide fuel cells (SOFCs) are compromised due to the difference in material densities between dense connecting members and porous air electrodes, particularly under mechanical and thermal stresses.
Innovation Solution
The use of dense conductive ceramics for both conductive members and a metallic connecting member with a connecting material of electron conductivity ensures high connection strength and reliability, with the conductive ceramics having a porosity of 15% or less, and the air electrode being supported by conductive ceramics of the same material as the fuel electrode for enhanced connection strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous air electrode is connected to a dense connecting member with a connecting material, then electrical connection is achieved, but connection strength and reliability decrease due to material density difference
Solution Approach 1:
The patent introduces a dense conductive ceramics layer as an intermediary between the porous air electrode and the connecting member. This intermediate layer acts as a mediator that bridges the material density difference, providing a dense surface for reliable connection while maintaining electrical conductivity. The dense conductive ceramics layer is formed by screen printing a paste containing conductive ceramics powder and sintering it, creating a transition zone that resolves the contradiction between porosity needed for electrode function and density needed for connection strength.
2Strength
If dense materials are connected to each other, then high connection strength is achieved, but the air electrode's porous structure cannot be utilized
Solution Approach 1:
The patent applies local quality by creating different structural characteristics in different regions of the air electrode. The region contacting the connecting member is made dense through the conductive ceramics layer for high connection strength, while the bulk of the air electrode maintains its porous structure for electrical function. This localized differentiation allows each region to optimize its properties for its specific function, resolving the contradiction between density for strength and porosity for electrical performance.
3Productivity
If porous materials are used for air electrode, then gas permeability is improved, but connection strength with dense connecting member decreases
Solution Approach 1:
The patent segments the air electrode structure into functionally distinct regions: a porous bulk region for gas permeability and electrical conduction, and a dense surface layer (conductive ceramics layer) for mechanical connection. This segmentation allows the porous structure to be preserved in the bulk for maintaining gas flow and electrical performance, while the dense surface layer provides the necessary mechanical strength for connection to the connecting member.
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
This configuration provides a connected body with high connection strength and reliability, maintaining electric connection integrity under stress conditions and enhancing power generation efficiency.
Implementation Method 1
a first conductive member which is electrically connected to the fuel electrode of the first power generation part and is formed of a dense conductive ceramics having electron conductivity; a second conductive member which is electrically connected to the air electrode of the second power generation part and is formed of a dense conductive ceramics having electron conductivity
Data Source
AI summary
Adjacent two segmented-in-series type SOFCs (100), (100) are connected to each other with a metallic connecting member (300). A "left side end portion of the connecting member (300)" and an "interconnector (30) electrically connected to an air electrode (60) provided on the SOFC (100) on the left side" are electrically connected to each other with a connecting material (80), and a "right side end portion of the connecting member (300)" and the "interconnector (30) electrically connected to a fuel electrode (20) provided on the SOFC (100) on the right side " are electrically connected to each other with the connecting material (80). Both of the interconnectors (30), (30) to be respectively connected to both ends of the metallic connecting member (300) with the connecting material (80) are formed of dense conductive materials. Provided is a connected body connecting electrically between power generation parts of SOFCs, which has high connection strength and high reliability of electric connection.