Porous Electrode Interconnect Contacts for Solid-Oxide Fuel Cells
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Solution Overview
Problem
Existing solid-oxide fuel cell (SOFC) stacks face issues with poor adhesion and porosity of interconnects to electrodes, leading to reduced efficiency and longevity due to densification of contact pastes during sintering, which limits gas permeability and reactant availability at the triple phase boundary.
Innovation Solution
Incorporating sacrificial pore-forming particles in the contact pastes for both anode and cathode, allowing for higher porosity and improved adhesion through altered sintering processes and application methods, such as increased temperature and continuous layer formation, to maintain electrical conductivity and gas permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If contact paste is sintered at high temperature to ensure bonding, then adhesion strength is improved, but porosity is reduced and gas permeability is blocked
Solution Approach 1:
The patent applies porous anode contact paste containing nickel oxide particles with controlled porosity (30-70% void volume) that maintains gas permeability while providing adequate adhesion. The porous structure allows fuel gas to penetrate through the contact paste layer to reach the triple phase boundary, resolving the contradiction between adhesion strength and gas permeability.
Solution Approach 2:
The patent changes the chemical and physical parameters of the contact paste by using nickel oxide (NiO) instead of metallic nickel, and controlling the particle size distribution (0.1-10 micrometers) and porosity. These parameter changes enable the paste to maintain both adhesion and gas permeability at operating temperatures, avoiding the densification that occurs with conventional high-temperature sintering of metallic particles.
2Reliability
If grid pattern is fired at high temperature to ensure bonding, then electrical conductivity is improved, but porosity is reduced and fuel supply is starved
Solution Approach 1:
The patent uses a porous grid pattern formed by screen printing nickel oxide paste, maintaining 30-70% porosity after firing. This porous structure ensures both electrical conductivity for electron transport and sufficient fuel gas penetration to the reaction zone, resolving the contradiction between electrical conductivity and fuel supply.
Solution Approach 2:
The patent creates a composite structure where nickel oxide particles are distributed in a porous matrix, combining the electrical conductivity of metal oxide with the gas permeability of porous structure. This composite approach allows the grid to simultaneously conduct electricity and allow fuel penetration, eliminating the trade-off between these two functions.
3Strength
If contact paste is densified to improve adhesion, then bond strength is improved, but triple phase boundary accessibility is reduced
Solution Approach 1:
The patent changes the oxidation state parameter by using nickel oxide (NiO) instead of metallic nickel, and controls particle size (0.1-10 micrometers) and porosity (30-70%). These parameter changes enable the contact paste to achieve adequate bond strength while maintaining open pore structures that ensure reactant gas can reach the triple phase boundary, avoiding the densification problem of conventional pastes.
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 improved contact pastes enhance adhesion and porosity, leading to increased fuel and oxygen transport, reduced concentration polarization, and extended cell longevity by maintaining efficient electrochemical reactions and gas exchange.
Implementation Method 1
Incorporating sacrificial pore-forming particles in the contact pastes for both anode and cathode, allowing for higher porosity and improved adhesion through altered sintering processes
Implementation Method 2
allowing for higher porosity and improved adhesion through altered sintering processes and application methods, such as increased temperature
Data Source
Figure 1
AI summary
An electrical interconnect for a solid-oxide fuel cell stack assembly, including a novel sintering paste and an improved manufacturing process for an anode and cathode electrical contacts is disclosed. On the anode side, the paste contains a metallic oxide such as NiO, and an amount of sacrificial pore-forming particles, such as carbon particles or polymer spheres, which are vaporized during sintering of the paste, resulting in a very porous connection having good electrical conductivity and good adhesion. A preferred level of pore-former in the paste is about 40 volume percent. On the cathode side, the paste contains a noble metal such as for example, gold, platinum, palladium or rhodium, and an amount of the sacrificial pore-forming particles. The paste may be applied to the surfaces in a grid pattern or, because the resulting contact is porous after sintering, it may be applied as a continuous layer.