Monolithic Ceramic SOFC Stack With Embedded Gas Channels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid oxide fuel cell (SOFC) stacks face challenges such as high production costs, limited operational temperature, and mechanical instability due to metallic interconnects, which result in reduced power generation and shorter lifespan, along with complexities in material selection and fabrication processes.
Innovation Solution
A monolithic ceramic SOFC stack design is developed, featuring a stack scaffold with bulk and functional electrode scaffolds, thin ceramic interconnects, and embedded gas channels, where electrochemically active catalysts are infiltrated into porous electrode scaffolds, forming a rigid, all-ceramic structure that eliminates the need for metal interconnects and glass seals, and allows for uniform thermal expansion and sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If metallic interconnects are used in SOFC stacks, then electrical conductivity is improved, but mechanical stability and lifespan deteriorate due to thermal expansion mismatch and oxidation
Solution Approach 1:
The patent changes the material parameter from metallic to ceramic interconnects, specifically using gadolinium-doped ceria (GDC) which maintains electrical conductivity while providing thermal and chemical stability. This parameter change resolves the contradiction by eliminating oxidation issues and thermal expansion mismatch that plague metallic interconnects.
Solution Approach 2:
The patent employs composite material structures where GDC ceramic interconnects are integrated with electrode and electrolyte layers. The composite design allows optimization of each layer's properties - the GDC provides ionic conductivity and structural stability, while electrode composites provide catalytic activity and electron conduction, achieving both electrical conductivity and mechanical reliability.
2Reliability
If complex multi-layer structures are used to meet electro-chemical and mechanical requirements, then performance is improved, but fabrication complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into the GDC interconnect layer itself - it serves as both the structural support and the ion-conducting pathway. By combining the interconnect and electrolyte functions into a single GDC-based structure, the patent reduces the number of separate layers and simplifies fabrication while maintaining electro-chemical performance.
Solution Approach 2:
The GDC ceramic material performs multiple functions simultaneously: it provides mechanical support as an interconnect, conducts oxygen ions as an electrolyte, and offers thermal expansion compatibility. This multi-functionality reduces the need for separate specialized layers, simplifying the overall structure and fabrication process.
3Strength
If high sintering temperatures are used to achieve good diffusion bonding, then mechanical strength is improved, but material compatibility and component degradation worsen
Solution Approach 1:
The patent changes the sintering temperature parameter to an optimized range of 900-1100°C for GDC-based materials. This temperature is sufficiently high to achieve good diffusion bonding and mechanical strength, yet low enough to prevent formation of insulating phases and degradation of fuel cell components, resolving the contradiction between bonding strength and material compatibility.
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 design reduces production costs, enhances mechanical strength and electrical conductivity, increases operational temperature, and extends the lifespan of SOFC stacks while simplifying the assembly process, leading to improved power density and efficiency.
Implementation Method 1
an oxygen ion conducting metal oxide derived ceramics as the electrolyte... Under differential oxygen partial pressure between the two sides of electrolyte, oxygen ions are transported from cathode to the anode
Implementation Method 2
electrodes must be composed of materials... capable of catalyzing the electro-chemical reactions... electrodes should have sufficient porosity to allow gas diffusion and provide sufficient triple phase boundary sites facilitating the chemical reactions
Implementation Method 3
The electrode and electrolyte can be individually deposited to the anode support and fired in sequence, or they can be formed and fired with the anode support... high sintering temperatures, such as >1300° C., are often required to achieve good diffusion bonding between layers
Implementation Method 4
anode, cathode, and electrolyte materials generally have different thermal expansion coefficients (CTE) that can result in excessive internal stress during post sinter cooling down or thermal cycle... formed of certain composition and microstructure to achieve similar CTE to electrolyte
Data Source
AI summary
A design of and the process for forming a monolithic electrode supported electro-chemical device is provided. The electro-chemical device stack can be a solid oxide fuel cell stack. The monolithic stack comprises multiple planar cells connected in serial by planar ceramic interconnects. The cells have gas channels embedded in electrode layers in both anode and cathode sides. Thin ceramic electrolyte and interconnect are sandwiched between electrodes. The process comprises the steps of a). forming green cells by laminating green tapes of anode, electrolyte, and cathode, b). forming a green stack by laminating cells and interconnects, c). firing the green stack to form a stack scaffold, d). covering the stack exterior surfaces with a hermetic coating, and f). infiltrating catalysts into porous electrodes through gas channels to form an active stack.