Fuel Cell Contact Element Thermal Expansion Mismatch
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Solution Overview
Problem
High-temperature fuel cells face issues with electrical conductivity and thermal expansion, leading to mechanical strain and reduced power output due to nickel current collectors, which result in increased electrical resistance and 'hot spots', affecting the reliability of the connection between the anode and interconnector.
Innovation Solution
A contact element with two areal electrically conductive part elements, each with different coefficients of thermal expansion, is designed to be porous and deformable, allowing fuel passage and distributing compressive strains to stabilize the electrical contact, with openings arranged for optimal fuel exchange and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel current collectors are used to provide electrically conductive connection, then electrical conductivity is improved, but thermal expansion mismatch causes mechanical strain and contact failure
Solution Approach 1:
The patent changes the material parameter (coefficient of thermal expansion) by replacing pure nickel with a composite material containing nickel and inconel. This parameter change allows the contact element to match the thermal expansion characteristics of the solid electrolyte, eliminating the mismatch that causes mechanical strain and contact failure during temperature cycling.
Solution Approach 2:
The patent employs a composite material structure combining nickel and inconel in specific proportions (30-70 wt% nickel, 70-30 wt% inconel). This composite approach leverages the electrical conductivity of nickel while incorporating the thermal expansion compatibility of inconel with ceramic electrolytes, thus resolving the contradiction between electrical conductivity and thermal expansion mismatch.
2Stress or pressure
If nickel current collector thickness is reduced, then thermal stress is decreased, but mechanical strain and production tolerances cannot be compensated
Solution Approach 1:
The composite material structure provides both reduced thermal stress (due to better thermal expansion matching) and sufficient mechanical strength (through the combined properties of nickel and inconel). This eliminates the need to compromise between thickness reduction for stress relief and maintaining adequate ductility for strain compensation.
Solution Approach 2:
By changing the material composition parameters, the contact element achieves optimal balance between mechanical strength and thermal stress resistance, allowing for adequate thickness that satisfies both requirements simultaneously rather than requiring trade-offs.
3Quantity of substance
If net or fiber structure current collectors are used, then permeability is improved, but local deformation creates hot spots and increased electrical resistance
Solution Approach 1:
The patent employs a porous or net structure in the contact element to ensure adequate fuel permeability. The porous design allows fuel to pass through while maintaining structural integrity, preventing the local deformation and hot spot formation that occur with conventional net structures.
Solution Approach 2:
The composite material structure provides enhanced mechanical stability that prevents local deformation during operation. This stability ensures uniform current distribution across the contact surface, eliminating the hot spots and electrical resistance increases that plague conventional net or fiber structure current collectors while maintaining necessary fuel permeability.
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 provides a more reliable and stable electrically conductive connection between the anode and interconnector, maintaining high electrical conductivity and reducing thermal stress, thereby improving the performance and longevity of high-temperature fuel cells.
Implementation Method 1
Both part elements are formed from materials each having mutually different coefficients of thermal expansion. Deformations occur on a temperature change due to the different coefficients of thermal expansion.
Implementation Method 2
Openings are formed in the part elements via which the fuel can pass through the contact element and the contact element is permeable for this purpose.
Data Source
AI summary
The invention relates to a contact element for an electrically conductive connection between an anode and an interconnector of a high-temperature fuel cell. It is the object of the invention to achieve a more reliable electrically conductive connection with long-term stability between an anode and the associated interconnector of a high-temperature fuel cell. The contact element in accordance with the invention is arranged between an anode and an interconnector of a high-temperature fuel cell. It is formed with two areal electrically conductive part elements. In this respect, one respective part element is in touching contact with the anode and the other part element is in touching contact with the respective interconnector. Openings are formed in the part elements and the part elements are formed from materials having mutually different coefficients of thermal expansion.