Alkaline Cation Conductive Ceramic Membrane Coating
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Solution Overview
Problem
Rechargeable metal-air batteries face limitations in mass energy density due to the reactivity of metallic lithium or sodium with water, leading to a significant increase in cationic resistance at the solid electrolyte/aqueous electrolyte interface, where a dense crystalline layer of alkali metal hydroxide forms, hindering conductivity.
Innovation Solution
A ceramic membrane conductive to alkaline cations is coated with a thin layer of an insoluble and chemically stable cation-conductive organic polymer, preventing the formation of a dense crystalline layer of alkali metal hydroxide at the interface, thereby maintaining high conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic membrane conductive to alkaline cations is used to separate metallic lithium or sodium from aqueous electrolyte, then the reactivity between metal and water is prevented, but a dense crystalline layer of alkali metal hydroxide forms at the interface, significantly increasing cationic resistance
Solution Approach 1:
A thin layer of hydrophobic organic polymer is introduced as an intermediary between the ceramic membrane and the aqueous electrolyte. This polymer layer prevents direct contact between the aqueous environment and the ceramic surface, thereby preventing the formation of the dense crystalline hydroxide layer that causes high resistance, while still allowing cationic conduction to occur through the polymer matrix.
Solution Approach 2:
The invention changes the chemical and physical parameters at the interface by coating the ceramic membrane with a hydrophobic polymer. This modification alters the surface properties from hydrophilic to hydrophobic, preventing water and hydroxide crystallization while maintaining cationic conductivity through the modified interface structure.
2Quantity of substance
If the concentration of alkali metal hydroxide in the aqueous electrolyte is increased to improve mass energy density, then the battery capacity increases, but precipitation of metal hydroxide occurs, limiting further concentration increase
Solution Approach 1:
The hydrophobic polymer layer acts as a barrier that prevents the precipitation of metal hydroxide at the ceramic membrane interface. By blocking the interface where crystallization normally occurs, the polymer allows much higher concentrations of alkali metal hydroxide to be maintained in the aqueous electrolyte without precipitation, thereby enabling higher mass energy density.
3Object-affected harmful factors
If a thin layer of hydrophobic organic polymer is coated on the ceramic membrane surface, then the formation of dense crystalline hydroxide layer is prevented and cationic conductivity is maintained, but the device complexity increases
Solution Approach 1:
A thin film of hydrophobic organic polymer is applied to the ceramic membrane surface. This thin film coating approach maintains the structural integrity and functionality of the original ceramic membrane while adding only a minimal layer that provides the necessary hydrophobic protection. The simplicity of the thin film application process helps minimize the increase in device complexity.
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 enhances the cationic conductivity and prevents the undesirable crystallization of alkali metal hydroxide, improving the energy efficiency and lifespan of rechargeable metal-air batteries by maintaining low resistance and allowing for higher alkali metal hydroxide concentrations without precipitation issues.
Implementation Method 1
a membrane of solid electrolyte conducting alkaline cations
Implementation Method 2
a thin layer of an insoluble and chemically stable cation-conductive organic polymer... which is hydrophobic
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to an alkaline cation-conducting ceramic membrane covered, over at least a portion of the surface thereof, with a cation-conducting organic polyelectrolyte layer that is insoluble and chemically stable in pH-basic water. The invention also relates to an electrochemical device including such a membrane as a solid electrolyte in contact with a liquid electrolyte formed of an alkali metal hydroxide aqueous solution.