Argyrodite Solid Electrolyte With Controlled Crystallite Size
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Solution Overview
Problem
Current solid electrolytes for solid-state batteries often suffer from inadequate lithium ion conductivity and battery characteristics due to the presence of lithium sulfide and thermodynamically stable crystal phases that impede ion migration and battery performance.
Innovation Solution
A solid electrolyte with an argyrodite-type crystal structure, comprising lithium, phosphorus, sulfur, and a halogen, is produced through a calcination and crushing process that maintains the meta-stable argyrodite phase, ensuring high lithium ion conductivity and improved battery characteristics by controlling the molar ratios and crystallite size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte with argyrodite-type crystal structure is used, then lithium ion conductivity is improved, but the crystal phase tends to transform to thermodynamically stable phases that reduce ion migration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molar ratios of Li, P, S, and halogen elements in the solid electrolyte composition. By adjusting these compositional parameters and controlling calcination temperature and crushing energy, the patent stabilizes the meta-stable argyrodite phase while maintaining high lithium ion conductivity, preventing transformation to thermodynamically stable phases that would reduce performance
Solution Approach 2:
The patent employs preliminary action through the calcination process that pre-forms the argyrodite-type crystal structure before final product formation. By performing calcination at controlled temperatures followed by specific crushing operations, the desired crystal phase is established in advance, preventing subsequent unwanted phase transformations during battery operation
2Reliability
If lithium sulfide is present in the solid electrolyte, then the argyrodite phase can be formed, but lithium sulfide impedes lithium ion migration and reduces battery performance
Solution Approach 1:
The patent applies the extraction principle by removing excess lithium sulfide from the solid electrolyte composition through controlled calcination and crushing processes. The method extracts only the necessary amount of lithium sulfide required to form the argyrodite structure while eliminating the harmful excess that would impede ion migration and reduce battery performance
Solution Approach 2:
The patent uses parameter changes by optimizing the initial molar ratios of reactants and controlling the calcination temperature and duration to precisely regulate the amount of lithium sulfide formed. This ensures sufficient lithium sulfide for argyrodite phase formation while preventing excessive lithium sulfide that would harm battery performance
3Reliability
If the crystallite size is reduced to enhance ion migration, then lithium ion conductivity improves, but the mechanical strength and stability of the solid electrolyte may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the crushing energy applied to the calcined product. By controlling the crushing energy parameter within a specific range, the patent achieves sufficient crystallite size reduction to enhance lithium ion conductivity while maintaining adequate mechanical strength and structural stability of the solid electrolyte
Solution Approach 2:
The patent employs partial action by applying a controlled amount of crushing energy that is sufficient to reduce crystallite size for improved ion migration but not excessive to the point of compromising mechanical integrity. This balanced approach achieves the optimal trade-off between conductivity enhancement and structural stability
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 resulting solid electrolyte exhibits enhanced lithium ion conductivity and improved battery performance, including increased output characteristics and durability, by minimizing the presence of lithium sulfide and stabilizing the argyrodite phase, which favors lithium ion migration and contact with active materials.
Implementation Method 1
a calcination step of calcining a raw material composition at 200° C. or more to obtain a calcined product
Implementation Method 2
a crushing step of crushing the calcined product by applying a crushing energy E represented by the following equation (1) of 200 J·sec/g or more to the calcined product
Implementation Method 3
the crystal phase that has an argyrodite-type crystal structure has a crystallite size of 40 nm or less... which favors lithium ion migration
Data Source
AI summary
A solid electrolyte contains a lithium (Li) element, a phosphorous (P) element, a sulfur (S) element, and a halogen (X) element. The solid electrolyte has a crystal phase that has an argyrodite-type crystal structure. The crystal phase that has an argyrodite-type crystal structure has a crystallite size of 40 nm or less. The solid electrolyte satisfies a ratio Ia/Ib of 0.2 or less, where Ia represents the intensity of a peak A observed in a range of 2θ=27.0°±0.5° in an XRD pattern, and Ib represents the intensity of a peak B observed in a range of 2θ=25.5°±1.0° in the XRD pattern.