Porous Solid Electrolyte Electrode for Limiting Current Oxygen Sensing

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Solution Overview

Problem

Conventional limiting current type gas sensors using solid electrolytes require a separate porous membrane, leading to complex production processes and increased lead time.

Innovation Solution

A solid electrolyte assembly with a first electrode containing a porous material and a single or multiple oxygen diffusion paths, where the ratio of the smallest cross-sectional area to the overlapping area (Sr/Sp) is optimized to eliminate the need for a separate porous membrane, simplifying the structure and reducing production time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate porous membrane is used to limit oxygen gas supply, then the limiting current function is achieved, but the device complexity and production time increase

Engineering Contradiction:

Improvelimiting current functionVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the porous membrane function with the electrode structure by making the first electrode itself porous. This integration eliminates the need for a separate porous membrane layer, reducing structural complexity while maintaining the limiting current function through controlled oxygen diffusion via the porous electrode material.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The first electrode is designed to serve multiple functions: it acts as both the electroactive electrode and the oxygen diffusion limiting structure. By incorporating porosity into the electrode, it simultaneously performs electron transfer and mass transport control, eliminating the need for dedicated separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a separate porous membrane is used to limit oxygen gas supply, then the limiting current function is achieved, but the production time increases

Engineering Contradiction:

Improvelimiting current functionVSAvoidproduction lead time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts the oxygen diffusion limiting function from the separate porous membrane and transfers it to the electrode structure itself. By making the electrode porous, the limiting function is embedded within the electrode, eliminating the need for additional membrane formation steps.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If the first electrode is made porous to enable oxygen diffusion, then the production process is simplified, but the control precision over oxygen supply may be reduced

Engineering Contradiction:

Improveproduction process simplicityVSAvoidoxygen diffusion control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent controls oxygen diffusion by adjusting parameters of the porous electrode such as porosity, pore size distribution, and thickness. By optimizing these parameters, the electrode provides both simplified manufacturing (as a single component) and precise control over oxygen supply to maintain manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The porous electrode structure can have spatially varying properties, with different porosity or pore size in different regions. This allows localized control of oxygen diffusion rates, enabling precise control of oxygen supply while maintaining the simplified single-component structure.

Inventive Principle:

Principle #3Local quality

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 enables a linear relationship between current value and oxygen concentration, allowing for oxygen concentration measurement at low temperatures and voltages, while suppressing sensor deterioration and reducing production complexity.

Implementation Method 1

the first electrode has only one oxygen diffusion path that is formed overlapping the substrate and the solid electrolyte

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

the solid electrolyte has oxide ion conductivity

Methodology Applied

Scientific EffectIon conductivity: Conduction (electrical)

Data Source

PatentUS12480909B2Solid electrolyte, electrochemical element, and limiting current type gas sensor

Publication Date: 2025.11.25 MITSUI MINING & SMELTING CO LTD

AI summary

A solid electrolyte assembly includes a substrate, a solid electrolyte, and a first electrode and a second electrode. The solid electrolyte has oxide ion conductivity, and the first electrode is located under the solid electrolyte and contains a porous material. The first electrode has only one oxygen diffusion path that is formed overlapping the substrate and the solid electrolyte. When Sr represents the smallest cross-sectional area that is a cross-sectional area of the oxygen diffusion path at a location where the area of a cross section of the first electrode taken perpendicularly to an oxygen diffusing direction is smallest in a portion of the oxygen diffusion path where the oxygen diffusion path overlaps the substrate and the solid electrolyte in a plan view of the solid electrolyte assembly, and Sp represents the area of a region where the first electrode and the second electrode overlap each other in a plan view of the solid electrolyte, Sr/Sp is from 1×10−7 to 6.9×10−4.