Graded Ceramic Separator for High-Temperature Cells
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Solution Overview
Problem
High temperature rechargeable electrochemical cells face mechanical and thermal stresses, and existing sealing materials are prone to corrosion and bond failure due to thermal expansion mismatches and limited durability, leading to cell failure.
Innovation Solution
A graded integral structure for the electrolyte separator, comprising an ion-conducting ceramic at one end and an electrically insulating ceramic at the other, with a difference in thermal expansion coefficient of less than 5 parts per million per degree Celsius, and incorporating a strengthening agent to minimize stress and eliminate the need for sealing materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealing materials are used to join ceramic parts, then the cell can be assembled, but the sealing material has limited life and bond failure causes cell failure
Solution Approach 1:
The invention removes the sealing material from the system entirely by directly bonding dissimilar ceramic parts together, eliminating the component with limited life and preventing bond failure that causes cell failure
Solution Approach 2:
The invention bonds dissimilar ceramic materials (beta-alumina and beta''-alumina) directly together without intermediate sealing materials, creating a reliable joint between materials with different properties
2Ease of manufacture
If ceramic parts with dissimilar thermal expansion coefficients are bonded, then the cell structure is formed, but thermal stress causes cracking
Solution Approach 1:
The invention changes the bonding parameters by using low-temperature bonding methods and intermediate layers that accommodate thermal expansion differences, allowing dissimilar ceramics to be joined without cracking during temperature cycling
3Ease of manufacture
If glassy sealing material is used, then ceramic parts can be joined, but corrosion leads to bond failure
Solution Approach 1:
The invention removes the glassy sealing material from the system and replaces it with corrosion-resistant ceramic-to-ceramic bonding, eliminating the corrosion mechanism that leads to bond failure
Solution Approach 2:
The invention uses homogeneous ceramic materials for bonding (beta-alumina to beta''-alumina) rather than dissimilar materials with glassy sealants, creating a chemically compatible joint that resists corrosion
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 graded integral structure reduces the likelihood of cell failure by minimizing mechanical and thermal stresses and eliminating corrosion issues, resulting in a longer-lasting high temperature rechargeable electrochemical cell.
Implementation Method 1
a sodium-ion-conducting solid electrolyte. Suitable material includes beta-alumina and beta''-alumina, known together as beta-alumina solid electrolyte (BASE), which is used as the separator of electrodes
Implementation Method 2
The difference in the coefficient of thermal expansion of the ion-conducting first ceramic and the electrically insulating second ceramic is less than or equal to about 5 parts per million per degrees Centigrade. Bonded ceramic parts formed from dissimilar materials in a high temperature cell may crack due to thermal stress caused by mismatch in the coefficient of thermal expansion.
Implementation Method 3
sintering the green body at a temperature to form a graded integral structure comprising the ion-conducting first ceramic at a first end and the electrically insulating second ceramic at a second end
Data Source
AI summary
An electrolyte separator structure is provided. The electrolyte separator structure comprises a graded integral structure, wherein the structure comprises an ion-conducting first ceramic at a first end and an electrically insulating second ceramic at a second end, wherein the difference in the coefficient of thermal expansion of the ion-conducting first ceramic and the electrically insulating second ceramic is less than or equal to about 5 parts per million per degrees Centigrade, and wherein at least one of the first ceramic or the second ceramic comprises a strengthening agent. Method of making the ion-separator structure is provided. Electrochemical cells comprising the ion-separator structure and method of making the electrochemical cell using the ion-separator structure are also provided.