Perovskite Electrode Material for Solid Oxide Fuel Cells
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Solution Overview
Problem
Solid oxide fuel cells face issues with high electrical resistance and thermal expansion mismatch between current collecting layers and cathodes, leading to cracking and delamination, and existing materials like LaNi 1-x Fe x O 3 have low conductivity at high temperatures.
Innovation Solution
A new electrode material with a composition of La 1-s A s Ni 1-x-y-z Cu x Fe y B z O 3-δ, where A and B are selected from alkaline earth metals, transition metals, and rare earths, is developed, offering improved conductivity and thermal expansion matching, achieved through specific molar ratios and firing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If La 1-x Sr x CoO 3 is used as the current collecting layer material, then conductivity is improved, but coefficient of thermal expansion becomes extremely large (18-20 ppm/K) causing mismatch with cathode (12.5 ppm/K) and leading to cracking and delamination
Solution Approach 1:
The patent modifies the chemical composition parameters of the perovskite material by substituting multiple elements (Sr, Co, Fe, Ni, Cu) at different sites in the crystal structure. This multi-parameter compositional adjustment enables simultaneous optimization of electrical conductivity and coefficient of thermal expansion to match the cathode material, resolving the contradiction between these two properties.
Solution Approach 2:
The patent creates a composite perovskite material with multiple cation substitutions (La 1-x Sr x Ni 1-y Fe y O 3 with additional Co and Cu elements) that combines the beneficial properties of different metal oxides. This composite approach allows the material to achieve both high conductivity and appropriate thermal expansion characteristics that neither single-component material could provide alone.
2Stability of the object's composition
If LaNi 1-x Fe x O 3 is used as the current collecting layer material, then coefficient of thermal expansion is reduced (13.4-9.8 ppm/K) matching cathode better, but conductivity at 600-1000°C becomes low (not more than 700 S/cm)
Solution Approach 1:
The patent adjusts the stoichiometric ratios and substitution levels of multiple elements (Sr content x, Fe content y, plus Co and Cu additions) to fine-tune both the thermal expansion coefficient and electrical conductivity. By optimizing these compositional parameters within specific ranges, the material achieves the dual goal of thermal matching with cathode and sufficient high-temperature conductivity.
Solution Approach 2:
The patent designs a multi-functional perovskite material that simultaneously serves as both the current collecting layer and the connecting layer between cathode and separator. This material must perform multiple functions: provide electrical conductivity, match thermal expansion, and ensure stable operation at high temperatures, which is achieved through comprehensive compositional optimization.
3Reliability
If Pt paste is used as the connecting layer material, then conductivity is high, but cost becomes extremely high making it unsuitable for general purpose articles
Solution Approach 1:
The patent replaces expensive Pt paste with a cost-effective perovskite ceramic material (La 1-x Sr x Ni 1-y Fe y O 3 with Co and Cu substitutions) that can be synthesized from abundant raw materials. This substitution maintains the required electrical conductivity function while dramatically reducing material cost, making the fuel cell suitable for commercial applications.
Solution Approach 2:
The patent changes the material composition from precious metal-based (Pt) to base metal-based perovskite ceramic with optimized elemental ratios. By adjusting the composition parameters of the perovskite structure to achieve appropriate conductivity through electronic band structure modification rather than relying on precious metals, the cost is reduced while maintaining functional performance.
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 new material achieves high conductivity (800 S/cm or more at 750°C) with low thermal expansion (not more than 14.0 ppm/K), reducing electrical resistance and preventing delamination, while being cost-effective by avoiding expensive materials like Pt.
Implementation Method 1
the conductivity in air at 600 - 1000°C has a low value of not more than 700 S/cm
Implementation Method 2
exhibits improvement both in respect of coefficient of thermal expansion and conductivity
Implementation Method 3
the coefficient of thermal expansion (heat expansion ratio) of the current collecting layer material is 18 - 20 ppm/K
Data Source
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AI summary
A novel electrode that can be used at high temperature in air, a fuel cell using the material, and a method of manufacture of the same are provided. The electrode material containing a component expressed by La1-sAsNi1-x-y-zCuxFeyBzO3-δ (wherein, A and B are at least one element independently selected from the group consisting of alkaline earth metals, transition metals excluding Fe, Ni and Cu, and rare earths excluding La, and x>0, y>0, x+y+z<1, 0≤s≤0.05, and 0≤z≤0.05) exhibits relatively high conductivity at high temperature, and has the advantage of combination with other materials in relation to coefficient of thermal expansion.