SOFC Middle Layer Composition for Low Interfacial Resistance
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Solution Overview
Problem
In solid oxide fuel cells, the reaction between the solid electrolyte layer and the air electrode layer generates a high electric resistance, which hampers efficient power generation, and the middle layer's composition often contributes to this resistance.
Innovation Solution
A middle layer made of CeO2 with a rare earth element oxide, such as Sm or Gd, is introduced between the solid electrolyte layer and the air electrode layer, with a controlled molarity of Ce and Zr to minimize reaction and resistance, and is formed using physical/chemical vapor deposition methods like Pulsed Laser Deposition (PLD) or Ion Assist Deposition (IAD).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a middle layer is introduced between the solid electrolyte layer and the air electrode layer, then thermal compatibility with the support structure is improved, but electric resistance increases due to reaction between the solid electrolyte layer and the air electrode layer
Solution Approach 1:
The middle layer is designed with a specific composition (CeO2 with rare earth element oxide) that provides different properties at different locations: it offers thermal compatibility with the support structure while simultaneously preventing harmful reactions between the solid electrolyte layer and air electrode layer, thus resolving the contradiction between thermal stability and electrical resistance
Solution Approach 2:
The middle layer acts as an intermediary between the solid electrolyte layer and the air electrode layer, preventing direct contact and reaction between these two layers. This mediator layer eliminates the harmful reaction that would otherwise increase electric resistance, while maintaining thermal compatibility with the support structure
2Reliability
If the middle layer is made of CeO2 with rare earth element oxide, then reaction between solid electrolyte layer and air electrode layer is minimized, but manufacturing complexity increases due to controlled molarity requirements
Solution Approach 1:
The invention specifies precise molarity ranges for Ce (0.1-5.0 atomic ratio) and rare earth elements in the middle layer. By controlling these compositional parameters within defined ranges, the patent achieves effective reaction prevention while providing clear manufacturing guidelines that balance performance requirements 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
This configuration reduces the electric resistance between the solid electrolyte and air electrode layers, enhancing power generation efficiency by minimizing the formation of high-resistance components and maintaining thermal compatibility with the support structure.
Implementation Method 1
EP 3021393 A1 discloses a solid oxide fuel cell comprising a solid electrolyte layer, an air-electrode layer that contains at least strontium, a fuel-electrode layer, and an intermediate layer formed between the solid electrolyte layer and the air-electrode layer, wherein at least part of the intermediate layer contains an element-diffusion prevention layer including a complex oxide containing zirconium and at least one rare-earth element.
Implementation Method 2
EP 3 021 393 A1 describes a method for forming the intermediate layer by a physical vapor deposition method or a chemical vapor deposition method
Implementation Method 3
EP 3 021 393 A1 describes a method for forming the intermediate layer by a physical vapor deposition method or a chemical vapor deposition method
Data Source
Figure 1A~1B
Figure 2~3A
Figure 3B
AI summary
A cell 1 according to the present disclosure includes: a first electrode layer (3); a solid electrolyte layer (4) on the first electrode layer (3), the solid electrolyte layer (4) containing Zr; a middle layer (7) on the solid electrolyte layer (4), the middle layer (7) containing CeO2 which also contains a rare earth element other than Ce; and a second electrode layer (5) on the middle layer (7), wherein a boundary region between the solid electrolyte layer (4) and the middle layer (7) includes a basing point at which a molarity of Ce and a molarity of Zr are equal. An average molarity of the Ce within a range from the basing point up to 3 µm toward the solid electrolyte layer 4 is equal to or less than 10 mol% with respect to a total of Ce, Zr, and other rare earth elements, an average molarity of Zr within the range is equal to or more than 70 mol% with respect to a total of Ce, Zr, and other rare earth elements, or a molarity ratio of Ce with respect to Zr within the range is equal to or less than 0.143.