Solid Electrolyte Edge Gradient for Thermal Expansion Matching

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Solution Overview

Problem

The joint region between solid electrolytes and insulators in electrochemical cells, particularly those using β-alumina or β″-alumina and α-alumina, experiences defects due to differing thermal expansion coefficients, leading to potential leakage and reduced stability.

Innovation Solution

A solid electrolyte with a concentration gradient of α-alumina and β-alumina in its edge portion, matched to the thermal expansion coefficient of the insulator, is integrated with the main portion, and joined via a glass frit to minimize defects, with the edge portion being sintered to create a uniform thermal expansion profile.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a solid electrolyte made of β-alumina or β″-alumina is joined to an insulator made of α-alumina, then the electrochemical cell achieves high energy density and long lifetime, but joint region defects occur due to different thermal expansion coefficients

Engineering Contradiction:

Improvejoint stabilityVSAvoidthermal expansion mismatch

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The solid electrolyte is designed with a non-uniform composition: the edge portion (adjacent to insulator) has higher α-alumina content while the main portion has higher β-alumina content. This local quality variation allows the edge portion to match the thermal expansion coefficient of the insulator, preventing joint defects, while the main portion maintains the required electrochemical performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The solid electrolyte uses a composite material system combining α-alumina and β-alumina (or β″-alumina) in a gradient distribution. This composite structure enables simultaneous achievement of thermal expansion compatibility at the joint region and electrochemical functionality in the main body, resolving the contradiction between joint stability and material performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the concentration of α-alumina is increased in the solid electrolyte to match thermal expansion coefficients, then joint defects are prevented, but the electrochemical performance may be compromised

Engineering Contradiction:

Improvejoint region integrityVSAvoidelectrochemical cell power

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The invention applies local quality by concentrating α-alumina specifically in the edge portion where thermal expansion matching is critical, while keeping the main portion rich in β-alumina to maintain electrochemical performance. This spatial differentiation resolves the contradiction between joint integrity and power output.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the concentration parameter of α-alumina spatially within the solid electrolyte. By creating a concentration gradient (higher at edges, lower in center), the system achieves both thermal compatibility at joints and electrochemical efficiency in the bulk, preventing the need to sacrifice power for reliability.

Inventive Principle:

Principle #35Parameter changes

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

This configuration effectively prevents joint defects, ensuring stable operation and extended lifespan of the electrochemical cell by maintaining identical thermal expansion coefficients across the joint region, thereby reducing the likelihood of electrode material leakage.

Implementation Method 1

The edge portion may be integrally sintered with the main portion

Methodology Applied

Scientific EffectSintering: Sintering

Implementation Method 2

the two structures may have different thermal expansion coefficients... gradually increasing the concentration of α-alumina and gradually decreasing the concentration of β-alumina (or β′′-alumina) in the solid electrolyte in a direction towards the joint region... having substantially identical thermal expansion coefficient as that of the insulator

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

The edge portion may be joined to an insulator via a glass frit

Methodology Applied

Scientific EffectGlass frit bonding:

Data Source

PatentUS8962193B2Electrochemical cell with solid electrolyte having alumina edge portion

Publication Date: 2015.02.24 SAMSUNG SDI CO LTD

AI summary

A solid electrolyte is disclosed. The solid electrolyte includes a main portion that includes β-alumina or β″-alumina, and an edge portion integrally provided with the main portion. The edge portion has a mixed portion that includes α-alumina and includes β alumina or β″-alumina. A concentration gradient of the α-alumina in the edge portion decreases in a first direction from the edge portion to the main portion.