Fuel Cell Interconnect Alloy With Spinel Layer Against Chromium Evaporation
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Solution Overview
Problem
Chromium-based interconnects in solid oxide fuel cell stacks degrade due to chromium oxidation, leading to increased ohmic resistance and chromium poisoning of cathodes, which degrades the electrochemical activity and performance over time.
Innovation Solution
Incorporating a chromium-transition metal oxide spinel interfacial layer and a protective coating on the air side of the interconnects, formed by sintering an interconnect powder comprising Cr, Fe, and transition metals like Co, Cu, Mn, or V, to reduce chromium evaporation and increase electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium-based interconnects are used in solid oxide fuel cell stacks, then electrical connection and gas flow channels are provided, but chromium oxidation occurs leading to increased ohmic resistance and cathode poisoning
Solution Approach 1:
A protective coating layer comprising manganese oxide and/or cobalt oxide is applied over the air side of the interconnect body, serving as an intermediary barrier between the chromium-based alloy and the oxidizing environment. This coating layer prevents direct oxidation of chromium, thereby reducing chromium evaporation and cathode poisoning while maintaining electrical conductivity and structural integrity.
Solution Approach 2:
The interconnect structure is designed as a composite system consisting of a chromium-based alloy interconnect body with a chromium-transition metal oxide spinel interfacial layer and an outer protective coating layer. This multi-layer composite structure combines the electrical conductivity and mechanical strength of chromium-based alloys with the oxidation resistance of protective coatings, resolving the contradiction between reliability and harmful chromium evaporation.
2Object-generated harmful factors
If protective coating is applied to prevent chromium oxidation, then chromium evaporation is reduced, but manufacturing complexity increases
Solution Approach 1:
The concentration of transition metals (manganese and/or cobalt) is optimized within specific ranges (0.1-5 wt% each) to achieve the desired balance between protective function and manufacturing simplicity. The protective coating is designed with controlled thickness (1-10 micrometers) to provide adequate protection while minimizing added complexity and cost.
3Reliability
If transition metals are added to chromium-based alloy, then electrical conductivity is improved, but alloy composition control becomes more difficult
Solution Approach 1:
The alloy composition is precisely controlled with chromium at 85-95 wt%, iron at 3-10 wt%, and transition metals (manganese and/or cobalt) at 0.1-5 wt% each. These parameter ranges are optimized to maintain electrical conductivity while ensuring proper formation of the protective oxide layers during operation. The sum of manganese and cobalt content is controlled at 0.1-10 wt% to balance protective function with manufacturing feasibility.
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 chromium-transition metal oxide spinel interfacial layer significantly reduces chromium evaporation and increases electrical conductivity, thereby mitigating performance degradation and extending the lifespan of the fuel cell stack.
Implementation Method 1
sintering the interconnect
Implementation Method 2
a protective coating comprising an oxide of at least one of Mn or Co located over the air side of the interconnect body
Implementation Method 3
a chromium-transition metal oxide spinel interfacial layer located between the air side of the interconnect body and the protective coating
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
A method of making an interconnect for a fuel cell stack includes compressing an interconnect powder to form an interconnect, the interconnect power containing Cr, Fe and at least one transition metal selected from Co, Cu, Mn, Ni, or V pre-alloyed with at least one of the Cr and the Fe, and sintering the interconnect.