SOFC Anode Infiltration Sequence for Sulfur Poisoning Resistance
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Solution Overview
Problem
Solid oxide fuel cells (SOFCs) with Ni-based anodes are susceptible to sulfur poisoning and carbon-based degradation, and existing infiltration methods either compromise cell strength or are difficult to perform without causing cracking during stack fabrication.
Innovation Solution
Oxidize individual SOFCs before stacking, build the stack, reduce and then infiltrate the anodes with poison-preventing materials using vapor-phase or liquid solution permeation, eliminating the need for prior reduction/oxidation steps and maintaining cell strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode is reduced and then infiltrated prior to fabrication of the stack, then the anode becomes more robust to sulfur poisoning and carbon-based degradation, but the cell cracks during re-oxidation before stack fabrication
Solution Approach 1:
The patent inverts the conventional sequence by performing infiltration after stack fabrication instead of before. The anodes are reduced and infiltrated while stacked, then the entire stack is re-oxidized. This inversion eliminates the cracking problem because the stack structure provides mechanical support during re-oxidation, preventing the cells from cracking despite the anodes being in a reduced state during infiltration.
Solution Approach 2:
The patent merges multiple operations into a unified process. Instead of treating individual cells through separate reduction, infiltration, and re-oxidation cycles before stacking, the method combines these steps for the entire stack. The stack is reduced as a unit, infiltrated as a unit, and re-oxidized as a unit, which maintains structural integrity while achieving the desired anode protection.
2Ease of manufacture
If the anode porosity is increased to allow infiltration, then the anode can be infiltrated with poison-preventing materials, but the strength of the anode is reduced
Solution Approach 1:
The patent changes the oxidation state parameter of the anode rather than permanently altering its porosity structure. By cycling the anode through reduction (enabling infiltration) and re-oxidation (restoring strength), the method achieves infiltration capability without permanent loss of mechanical strength. The porosity remains sufficient for infiltration during the reduced state, but the anode regains full strength after re-oxidation.
3Ease of manufacture
If the cell is kept reduced during stack fabrication, then infiltration can be performed, but air must be excluded which complicates the sealing process with sintered glass seals
Solution Approach 1:
The patent performs preliminary infiltration of the anodes while they are in the reduced state, before the re-oxidation step. This preliminary action completes the infiltration process while the anodes are still in the optimal chemical state for material uptake. After infiltration is complete, the stack is then re-oxidized in a controlled manner, allowing air to be introduced safely once the infiltration function has been achieved.
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 method effectively protects SOFC anodes from poisons without compromising cell strength, is cost-effective, and simplifies the manufacturing process, as demonstrated by improved power density and reduced degradation rates with specific material combinations like ruthenium and cerium.
Implementation Method 1
c) reduce all the stacked SOFC anodes
Implementation Method 2
d) infiltrate all the stacked SOFC anodes with poison-preventing materials by either vapor-phase or liquid solution permeation
Implementation Method 3
a) oxidize all the individual SOFCs to be stacked before building a stack
Data Source
AI summary
A method for forming a solid oxide fuel cell stack from a plurality of individual solid oxide fuel cells, wherein the anodes of the solid oxide fuel cells are infiltrated by one or more materials for making the anodes less sensitive to sulfur poisoning and/or less subject to carbon degradation and/or for improving the electrochemical performance of the stack, the method comprising the steps of oxidizing the anodes of the individual solid oxide fuel cells before forming a stack, building a solid oxide fuel cell stack with all of the anodes in an oxidized state, reducing all of the anodes, and then infiltrating all of the anodes with at least one of the materials.