Graded SOFC Anode Mitigating Nickel Oxidation

Solution Overview

Problem

Solid oxide fuel cell anode electrodes suffer irreversible damage under conditions of fuel starvation due to oxidation of nickel at the three-phase boundary, leading to mechanical damage and increased resistance, which reduces stack performance.

Innovation Solution

The anode electrode comprises a cermet with a nickel-containing phase and a ceramic phase, where the first portion near the electrolyte has a lower porosity and nickel content than the second portion, and is annealed in a reducing atmosphere to maintain nickel in a reduced state, with a graded composition to mitigate stress and improve stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an all ceramic anode is used to avoid nickel oxidation and mechanical damage, then stability under fuel starvation conditions is improved, but polarization losses increase

Engineering Contradiction:

Improvestability under fuel starvation conditionsVSAvoidpolarization losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The anode is designed with a graded composition where the first portion (near electrolyte) has lower nickel content and lower porosity for stability, while the second portion (distal from electrolyte) has higher nickel content and higher porosity for reduced polarization losses. This local differentiation allows each region to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The anode combines nickel-containing phase (metallic) with ceramic phase (stable) in a graded distribution. The first portion has lower nickel-to-ceramic ratio providing oxidation resistance, while the second portion has higher nickel-to-ceramic ratio providing electrical conductivity and reduced polarization, creating a composite structure that balances both requirements.

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If traditional anode with high nickel content is used, then polarization losses are reduced, but oxidation of nickel and mechanical damage occur under fuel starvation

Engineering Contradiction:

Improvepolarization lossesVSAvoidstability under fuel starvation conditions

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The anode is designed with a graded composition where the first portion (near electrolyte) has lower nickel content and lower porosity for stability, while the second portion (distal from electrolyte) has higher nickel content and higher porosity for reduced polarization losses. This local differentiation allows each region to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The anode combines nickel-containing phase (metallic) with ceramic phase (stable) in a graded distribution. The first portion has lower nickel-to-ceramic ratio providing oxidation resistance, while the second portion has higher nickel-to-ceramic ratio providing electrical conductivity and reduced polarization, creating a composite structure that balances both requirements.

Inventive Principle:

Principle #40Composite materials

3Loss of energy

If nickel content is increased to improve electrical conductivity, then polarization losses decrease, but volume expansion during oxidation increases mechanical damage

Engineering Contradiction:

Improvepolarization lossesVSAvoidmechanical integrity during oxidation

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The anode is designed with a graded composition where the first portion (near electrolyte) has lower nickel content and lower porosity for stability, while the second portion (distal from electrolyte) has higher nickel content and higher porosity for reduced polarization losses. This local differentiation allows each region to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The anode is divided into two distinct portions with different compositions: the first portion near the electrolyte with lower nickel content to minimize oxidation-induced volume expansion, and the second portion distal from the electrolyte with higher nickel content to provide electrical conductivity. This segmentation allows each region to be optimized for its specific role.

Inventive Principle:

Principle #1Segmentation

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 anode electrodes exhibit improved stability and low polarization losses, maintaining performance even under extreme fuel starvation conditions, reducing degradation and extending the lifetime of the fuel cell stack.

Implementation Method 1

annealed in a reducing atmosphere to maintain nickel in a reduced state

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 2

enables the transport of negatively charged oxygen ions from the cathode flow stream to the anode flow stream

Methodology Applied

Scientific EffectIon transport: Ion Repulsion/Attraction

Implementation Method 3

The phase change from Ni metal to NiO is accompanied by a change in volume that causes mechanical damage

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 4

The phase change from Ni metal to NiO is accompanied by a change in volume

Methodology Applied

Scientific EffectPhase change: Phase Change

Data Source

PatentUS10622642B2Anode with remarkable stability under conditions of extreme fuel starvation

Publication Date: 2020.04.14 BLOOM ENERGY CORP

AI summary

A solid oxide fuel cell (SOFC) includes a cathode electrode, a solid oxide electrolyte, and an anode electrode having a first region located adjacent to a fuel inlet and a second region located adjacent to a fuel outlet. The anode electrode includes a cermet having a nickel containing phase and a ceramic phase. The first region of the anode electrode contains a lower ratio of the nickel containing phase to the ceramic phase than the second region of the anode electrode.