Solid Oxide Fuel Cell Interconnect Using Flexible Membrane
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Solution Overview
Problem
Existing solid oxide fuel cell (SOFC) interconnect systems face challenges in providing a mechanically robust and low-resistance electrical connection that endures thermal cycling, while also preventing stress and fracture due to thermal expansion mismatches and poor gas flow uniformity.
Innovation Solution
The interconnect system comprises a separator plate with nickel oxide and silver alloy pastes applied to the anode and cathode surfaces, respectively, which form metallic bonds upon sintering, providing a mechanically robust and low-resistance electrical connection, along with a compliant structure that accommodates part variations and thermal expansion mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid mounting plate is used for interconnect, then mechanical support is provided, but thermal expansion mismatch induces stress leading to cell fracture
Solution Approach 1:
The patent replaces rigid mounting plates with a flexible membrane structure that provides mechanical support while accommodating thermal expansion differences between components. The membrane's flexibility allows it to deform elastically during thermal cycling, preventing stress concentration and fracture at rigid connection points.
Solution Approach 2:
The patent changes the mechanical parameters of the interconnect structure by transitioning from rigid to flexible materials, and modifies the membrane tension parameters to optimize both support and compliance. This allows the system to maintain structural integrity while adapting to thermal expansion variations.
2Reliability
If contact paste is used for electrical connection, then electrical contact is achieved, but paste bonds fracture during thermal cycling resulting in poor connection
Solution Approach 1:
The patent removes the fragile contact paste layer from the electrical connection interface and replaces it with a direct wire bond connection. This extraction eliminates the paste's thermal cycling vulnerability while maintaining electrical conductivity through the more thermally stable wire bond.
Solution Approach 2:
The patent introduces a flexible membrane as an intermediary element between rigid components. This membrane serves as a stress-absorbing mediator that protects the electrical connection from thermal expansion-induced shear forces, allowing the connection to endure thermal cycling without bond fracture.
3Reliability
If a very flexible connecting filament system is used, then cell stress is reduced, but mechanical support is not provided and gas flow passages vary significantly
Solution Approach 1:
The patent employs a flexible membrane that operates in an optimized tension range to provide both mechanical support and stress accommodation. By controlling the membrane's physical parameters and pretension, it simultaneously supports cell weight and allows thermal expansion without excessive rigidity.
Solution Approach 2:
The patent optimizes the membrane's physical parameters including tension, thickness, and material properties to achieve the optimal balance between flexibility and support. This parameter optimization ensures uniform gas flow passages while maintaining cell stress reduction.
4Adaptability or versatility
If springy formed wire or sheet strips are used, then some compliance is provided, but mismatched spring forces create localized bending forces and stress
Solution Approach 1:
The patent replaces the non-uniform spring forces of discrete wire or strip elements with a homogeneous flexible membrane that distributes compliance uniformly across the entire interconnect surface. This eliminates localized bending moments and stress concentrations that arise from discrete spring elements.
Solution Approach 2:
The flexible membrane provides distributed compliance through its continuous structure, allowing uniform accommodation of surface irregularities and thermal expansion without creating the localized stress concentrations inherent in discrete springy elements.
5Ease of manufacture
If ferritic stainless steel separator plate is used, then cost is reduced and thermal expansion matches, but plate strength is insufficient and formed features creep
Solution Approach 1:
The patent replaces the weak ferritic stainless steel separator plate with a flexible membrane structure that derives its strength from tension rather than material yield strength. This allows the use of materials optimized for thermal expansion matching and cost while avoiding creep issues through the membrane's tensile load-bearing mechanism.
6Strength
If a stronger alloy is used for separator plate, then plate strength is improved, but thermal expansion mismatch creates severe shear forces that fracture contact paste joints
Solution Approach 1:
The flexible membrane eliminates thermal expansion mismatch shear forces by accommodating dimensional changes through elastic deformation rather than rigid resistance. This protects the electrical connection joints from fracture while maintaining structural integrity.
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 solution results in a durable, low-resistance interconnect system that withstands thermal cycling, minimizes cell stress, ensures uniform gas flow, and prevents chromium poisoning, while being cost-effective and simple to assemble.
Implementation Method 1
nickel oxide paste and silver alloy paste applied to the anode and cathode surfaces, respectively, which form metallic bonds upon sintering
Implementation Method 2
a compliant structure that accommodates part variations and thermal expansion mismatches
Data Source
AI summary
An interconnect system including: a separator plate to provide an anode gas flow space; a first metal interconnect disposed between the separator plate and an anode surface; a nickel oxide paste applied in a pattern over the surface of the anode and adjacent surface of the separator plate which when sintered results in a first conductive layer bonded to the anode and the first interconnect, and a second conductive layer bonded to the first interconnect and the separator plate; a second metal interconnect disposed between a cathode surface of the cell and the separator plate of an adjacent cell cassette; and a silver-containing paste applied over the surface of the cathode and the separator plate which when sintered results in a third conductive layer bonded to the cathode and the second interconnect, and a fourth conductive layer bonded to the second interconnect and the separator plate.