Argyrodite Solid Electrolyte Composition Beyond Halogen Limits
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Solution Overview
Problem
Current lithium solid-state battery technologies, particularly those using lithium argyrodites as solid electrolytes, face limitations in ionic conductivity and compatibility with high voltage cathodes and lithium metal anodes due to the restricted incorporation of halogen species like Cl, Br, and I.
Innovation Solution
The introduction of pseudo-halogen species such as BH4 and BF4 allows for the increase of the component 'X' in the lithium argyrodite formula, enhancing ionic conductivity beyond previous limits and improving electrochemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If halogen species (Cl, Br, I) are incorporated into lithium argyrodite structure, then ionic conductivity is improved up to a limit, but the maximum incorporation amount is restricted (y≤1.5 for Cl)
Solution Approach 1:
The patent changes the chemical nature of the anionic component from traditional halogens to pseudo-halogen species (BH4, BF4, NH2, NO3), which fundamentally alters the compositional parameters of the argyrodite structure. This parameter change enables the component X ratio to exceed the conventional y≤1.5 limit, achieving y>1.5 and significantly improving ionic conductivity while maintaining structural stability.
2Reliability
If higher oxidation potential species are used to improve electrochemical stability against high voltage cathodes, then compatibility with high voltage cathodes is improved, but the structural stability of argyrodite phase may be compromised
Solution Approach 1:
The patent creates a composite anionic structure by incorporating pseudo-halogen species (BH4, BF4, NH2, NO3) into the argyrodite framework. These pseudo-halogen species provide both high oxidation potential for electrochemical stability and appropriate ionic radius for structural compatibility. The composite nature of these species allows simultaneous achievement of electrochemical stability against high voltage cathodes and maintenance of argyrodite phase stability.
3Reliability
If the component X ratio is increased beyond conventional limits, then ionic conductivity is substantially improved, but the material may deviate from argyrodite-type structure
Solution Approach 1:
The patent utilizes parameter changes in the anionic component properties (using pseudo-halogen species with appropriate size and charge distribution) to enable higher component X ratios while preserving the argyrodite-type crystal structure. The pseudo-halogen species BH4, BF4, NH2, and NO3 have molecular dimensions and bonding characteristics that allow them to occupy the X sites in the argyrodite structure without disrupting the overall F-43m cubic symmetry, even at y>1.5 compositions.
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 approach results in an Argyrodite-type solid electrolyte with significantly improved ionic conductivity, exceeding 2 mS/cm, and enhanced compatibility with high voltage cathodes and lithium metal anodes, addressing the limitations of existing technologies.
Implementation Method 1
the lithium ion conductivity of argyrodite-type materials is correlated with the amount of component 'X' in the formula Li+(12-n-y)Tn+A2−(6-y)X−(y)
Data Source
AI summary
A solid electrolyte material comprising Li, T, X and A wherein T is at least one of P, As, Si, Ge, Al, and B; X is BH4; A is S, Se, or N. The solid electrolyte material may include glass ceramic and/or mixed crystalline phases, and exhibits high ionic conductivity and compatibility with high voltage cathodes and lithium metal anodes.