Fluoride Ion Conductor Composition for Room-Temperature Conductivity
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Solution Overview
Problem
Existing fluoride ion conductors have room for improvement in their ion conductivity, which is essential for enhancing the performance of fluoride ion batteries.
Innovation Solution
A fluoride ion conductor is developed with a composition formula A1-xAExM2F7+x, where A is an alkali metal, AE is an alkaline-earth metal, and M is a lanthanoid element, allowing partial replacement of alkali metal with alkaline-earth metal to introduce excessive fluoride ions into unstable sites, thereby improving ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fluoride ion conductors (such as BaR2F8 or KYb2F7) are used, then the material structure is stable, but the ion conductivity is low (on the order of 10^-3 S·cm^-1 at 800°C)
Solution Approach 1:
The patent employs composite material strategy by combining multiple elements (alkali metal A, alkaline-earth metal AE, and lanthanoid M) in a multi-component fluoride system A1-xAExM2F7+x. This composite approach creates synergistic effects where the interaction between different metal cations generates excessive fluoride ions and stabilizes the crystal structure, achieving high ion conductivity (≥10^-3 S·cm^-1 at 25°C) that exceeds conventional single-component fluoride conductors while maintaining structural stability
Solution Approach 2:
The patent applies parameter changes by systematically varying the composition parameters (ratios of A, AE, and M elements, and the stoichiometric parameter x) to optimize ion conductivity. By adjusting the content of alkaline-earth metal AE and controlling the fluoride excess parameter x in the range 0<x≤1, the invention achieves optimal balance between structural stability and ion transport properties, with peak conductivity observed at specific composition ranges
2Temperature
If the operating temperature is reduced from 800°C to room temperature, then the operational safety is improved, but the ion conductivity of conventional fluoride ion conductors decreases significantly
Solution Approach 1:
The patent achieves temperature-independent high ion conductivity by fundamentally changing the conduction mechanism through composition design. The multi-element fluoride system A1-xAExM2F7+x generates excessive fluoride ions that occupy unstable sites and form conduction pathways, enabling the material to maintain conductivity ≥10^-3 S·cm^-1 at 25°C without requiring high-temperature operation, thus decoupling the traditional trade-off between temperature and conductivity
Solution Approach 2:
The composite fluoride system combines alkali metal, alkaline-earth metal, and lanthanoid elements to create a synergistic structure that stabilizes the crystal lattice at low temperatures while maintaining high ion mobility. This composite approach prevents phase transitions and structural collapse that typically occur when reducing operating temperature in conventional fluoride conductors
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 new fluoride ion conductor exhibits significantly higher ion conductivity, enabling the development of high-performance fluoride ion batteries with improved electrical properties.
Implementation Method 1
fluoride ion conductor having high ion conductivity
Implementation Method 2
Anion Transport in BaR2F8 Crystals at Elevated Temperatures
Data Source
AI summary
A fluoride ion conductor is represented by the following composition formula (1): A1-xAExM2P7+x . . . (1) (wherein A=Na, K, Rb, Cs, or a combination thereof; AE=Ca, Sr, Ba, or a combination thereof; M=Sc, Y, Ln, (Ln is a lanthanoid element), Al, Ga, In, or a combination thereof; and 0<x<1). A fluoride ion battery includes the fluoride ion conductor as a solid electrolyte for fluoride ion batteries.