SOEC Interconnector Coating for Low Resistance and Cr Protection
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Solution Overview
Problem
The existing interconnectors for solid oxide electrochemical cell stacks face issues with high electrical resistance due to the formation of Cr2O3 oxide films, which degrade performance, and lack sufficient adhesiveness between the protective film and metal substrate, leading to potential peeling and increased resistance.
Innovation Solution
A protective film comprising a metal layer, an oxide layer, and a mixed layer is applied to the interconnector, where the metal layer contains a first metal element, the oxide layer consists of spinel or perovskite oxides, and the mixed layer has a first and second phase, improving adhesiveness and reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stainless alloy with high chromium content is used as the interconnector base, then high-temperature resistance is improved, but electrical conduction deteriorates due to Cr2O3 oxide film formation
Solution Approach 1:
The patent applies a multi-layer composite protective film structure consisting of a metal layer (containing Al, Si, or Ti), an oxide layer (containing spinel-type oxide like Co3O4 or perovskite-type oxide like LaCoO3), and a mixed layer. This composite structure prevents Cr2O3 formation on the stainless steel substrate while maintaining electrical conduction through the conductive oxide layer with mixed valence states.
Solution Approach 2:
The patent controls the oxidation state and composition of the oxide layer to maintain electrical conduction. By using oxides with mixed valence states (e.g., La1-xSrxCo1-yFeyO3) and controlling oxygen partial pressure during operation, the film maintains paramagnetic properties and electrical conductivity while protecting against Cr dispersion.
2Reliability
If a dense protective film is applied to prevent Cr dispersion, then Cr vaporization prevention is improved, but adhesiveness deteriorates leading to potential peeling
Solution Approach 1:
The patent creates different functional zones within the protective film: the metal layer provides strong adhesion to the substrate, the oxide layer provides Cr dispersion prevention and electrical conduction, and the mixed layer provides transition and bonding. Each layer has locally optimized properties for its specific function.
Solution Approach 2:
The multi-layer composite structure with metal layer, oxide layer, and mixed layer provides both strong adhesion and effective Cr protection. The mixed layer containing both metal and oxide phases creates a gradient structure that improves interfacial bonding while maintaining protective functions.
3Loss of energy
If a protective film is applied to maintain electrical conduction, then electrical resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The protective film structure is pre-formed on the interconnector before assembly into the electrochemical cell stack. The metal layer, oxide layer, and mixed layer are created in sequence during manufacturing, preparing the surface for optimal electrical and protective performance before operation.
Solution Approach 2:
The patent optimizes the thickness and composition parameters of each layer to balance electrical conduction and protective functions. The oxide layer thickness and metal element ratios are controlled to achieve the desired electrical resistance while maintaining structural integrity and adhesion.
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 proposed film structure enhances electrical conduction and adhesiveness, reducing the risk of peeling and lowering electrical resistance, thereby improving the efficiency and reliability of the solid oxide electrochemical cell stack.
Implementation Method 1
the oxide layer provided above the metal layer and including at least one oxide selected from the group consisting of a spinel-type oxide and a perovskite-type oxide... the at least one oxide containing a second metal element different from the first metal element
Implementation Method 2
Cr dispersion prevention is a function of preventing the Cr contained in the interconnector for the solid oxide electrochemical cell stack vaporizing under high-temperature working conditions to degrade the performance of the solid oxide electrochemical cell
Implementation Method 3
a mixed layer provided between the metal layer and the oxide layer, the mixed layer having a first phase and a second phase, the first phase including the first metal element, and the second phase including the at least one oxide
Data Source
Figure 1~2
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AI summary
An interconnector for a solid oxide electrochemical cell stack, includes: a metal substrate including an iron-based alloy containing chromium; and a protective film provided on the metal substrate in a first direction. The protective film includes: a metal layer provided on a surface of the metal substrate and containing a first metal element; an oxide layer provided above the metal layer and including at least one oxide selected from the group consisting of a spinel oxide and a perovskite oxide, the at least one oxide containing a second metal element different from the first metal element; and a mixed layer provided between the metal layer and the oxide layer and having a first phase and a second phase, the first phase including the first metal element, and the second phase including the at least one oxide.