Manganese Cobalt Spinel Coating for SOFC Interconnects

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Solution Overview

Problem

Solid oxide fuel cell (SOFC) interconnects made of chromium-containing alloys degrade due to chromia formation, leading to ohmic resistance and chromium poisoning of the cathode, which results in significant performance degradation.

Innovation Solution

Coating the interconnects with a manganese cobalt oxide spinel layer on the air side using a plasma spray process, which reduces the growth rate of the native chromium oxide layer and suppresses chromium vapor evaporation, thereby minimizing ohmic resistance and cathode degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If chromium-containing alloys are used for interconnects to maintain strength and dimensional stability at SOFC operating conditions, then mechanical properties are improved, but chromia formation occurs leading to ohmic resistance and cathode degradation

Engineering Contradiction:

Improvestrength and dimensional stabilityVSAvoidperformance degradation

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

A manganese-cobalt spinel coating layer is applied as an intermediary between the chromium-containing interconnect and the cathode. This coating suppresses chromium evaporation and reduces chromia formation, thereby preventing cathode degradation while maintaining the mechanical properties of the interconnect substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interconnect structure is designed as a composite system combining the chromium-containing alloy substrate with a manganese-cobalt spinel coating layer. This composite structure leverages the high strength and dimensional stability of the chromium alloy while the spinel coating provides protection against chromia formation and cathode poisoning.

Inventive Principle:

Principle #40Composite materials

2Object-generated harmful factors

If native chromium oxide layer forms on the interconnect surface, then chromium evaporation is suppressed, but ohmic resistance increases due to low electrical conductivity

Engineering Contradiction:

Improvechromium evaporationVSAvoidohmic resistance

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The manganese-cobalt spinel coating acts as an intermediary layer that controls chromium oxidation. It allows sufficient chromium evaporation suppression while maintaining lower ohmic resistance compared to thick native chromia layers, by providing a controlled barrier that manages both protection and electrical conductivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The coating changes the surface composition and oxidation behavior of the interconnect. By introducing manganese and cobalt elements, the surface forms a spinel structure with different electrical conductivity properties than native chromia, thereby reducing ohmic resistance while still preventing excessive chromium evaporation.

Inventive Principle:

Principle #35Parameter changes

3Loss of substance

If chromium reacts with water in humid air to form gaseous chromium oxide hydroxide, then chromium transport to cathode is enabled, but cathode performance degrades due to chromia deposition

Engineering Contradiction:

Improvechromium transportVSAvoidcathode performance

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The manganese-cobalt spinel coating serves as a protective intermediary between the chromium-containing interconnect and the cathode. It suppresses the formation of gaseous chromium oxide hydroxide by controlling surface oxidation, thereby preventing chromium transport to the cathode and avoiding cathode degradation from chromia deposition.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The coating converts the harmful effect of chromium reactivity into a beneficial outcome. By controlling the surface chemistry, it transforms the potential for harmful chromium vapor formation into a stable spinel surface structure that protects the cathode while maintaining interconnect functionality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 manganese cobalt oxide spinel coating significantly reduces the degradation rate of SOFC stacks by lowering ohmic resistance and preventing chromium poisoning, leading to improved long-term performance and durability.

Implementation Method 1

coating an air side of the interconnect substrate with a manganese cobalt oxide spinel coating using a plasma spray process

Methodology Applied

Scientific EffectPlasma spray: Plasma Spray

Implementation Method 2

suppresses chromium vapor evaporation, thereby minimizing ohmic resistance and cathode degradation

Methodology Applied

Scientific EffectEvaporation suppression: Evaporation

Data Source

PatentUS10446854B2Coatings for metal interconnects to reduce SOFC degradation

Publication Date: 2019.10.15 BLOOM ENERGY CORP

AI summary

A method of coating an interconnect for a solid oxide fuel cell includes providing an interconnect including Cr and Fe, and coating an air side of the interconnect with a manganese cobalt oxide spinel coating using a plasma spray process.