Sulfide Solid Electrolyte Crystallinity Without Lithium Instability
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Solution Overview
Problem
Conventional crystalline sulfide-based solid electrolytes require high-temperature heat treatment to achieve high crystallinity, leading to instability with lithium metal and increased electronic conductivity, which can cause side reactions and short circuits in all-solid-state batteries.
Innovation Solution
A Li2S—P2S5-MCl-MX′ (X′ being a halogen other than Cl) sulfide-based solid electrolyte with a specific molar ratio of elements, heat-treated at 450° C. to 500° C. under vacuum or inert atmosphere, minimizing sulfur vacancy and electronic conductivity while maintaining high ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If heat treatment temperature is increased to achieve high crystallinity, then crystallinity is improved, but stability with lithium metal deteriorates and electronic conductivity increases
Solution Approach 1:
The patent optimizes the heat treatment temperature parameter to a specific range (400-500°C) that achieves high crystallinity while preventing excessive electronic conductivity and maintaining stability with lithium metal. This parameter optimization resolves the contradiction by finding the optimal point in the temperature range that balances crystallinity formation with stability preservation.
2Stability of the object's composition
If heat treatment temperature is increased to achieve high crystallinity, then crystallinity is improved, but electronic conductivity increases causing side reactions
Solution Approach 1:
The patent controls the heat treatment temperature within a specific range (400-500°C) to achieve sufficient crystallinity while limiting electronic conductivity to acceptable levels. This parameter control prevents the harmful effect of excessive electronic conductivity that would cause side reactions, while still obtaining the desired crystalline structure.
3Ease of manufacture
If amorphous sulfide-based solid electrolyte is used to reduce manufacturing temperature, then manufacturing cost is reduced, but reactivity with lithium metal increases
Solution Approach 1:
The patent applies heat treatment at optimized temperatures (400-500°C) to transform the amorphous structure into a crystalline structure. This parameter change reduces the reactivity with lithium metal while maintaining manufacturing feasibility, as the heat treatment can be performed in standard equipment without requiring excessively high temperatures.
Solution Approach 2:
The patent utilizes the phase transition from amorphous to crystalline state through controlled heat treatment. This phase transition fundamentally changes the material properties, reducing reactivity with lithium metal while maintaining the benefits of lower manufacturing temperatures compared to traditional high-temperature crystallization methods.
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 solution provides a stable, high-crystallinity sulfide-based solid electrolyte with excellent lithium ion conductivity and low electronic conductivity, reducing the risk of short circuits and enabling efficient operation of all-solid-state batteries without the need for H2S gas.
Implementation Method 1
ions other than Li ions in such a solid electrolyte do not move, side reactions due to the movement of anions do not occur
Implementation Method 2
having low electronic conductivity while having excellent ionic conductivity
Implementation Method 3
heat treatment at a temperature of 500° C. or higher to achieve high crystallinity
Implementation Method 4
a crystalline sulfide-based solid electrolyte that has excellent ion conductivity, low electronic conductivity and excellent stability with respect to a lithium metal while having high crystallinity
Data Source
AI summary
The present invention relates to a sulfide-based solid electrolyte for an all-solid lithium secondary battery, and to a method for preparing the sulfide-based solid electrolyte. The present invention has an effect of providing a sulfide-based solid electrolyte that has excellent stability with respect to lithium metal and has excellent ion conductivity, while having high crystallinity. The present invention has an effect of providing a method for preparing a sulfide-based solid electrolyte that has excellent stability with respect to lithium metal and has excellent ion conductivity, while having high crystallinity even when heat-treated at a low temperature.