Argyrodite Sulfide Solid Electrolyte for Adhesion and Li-Ion Conductivity
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Solution Overview
Problem
Sulfide solid electrolytes with an argyrodite crystal structure face challenges in achieving good lithium ion conductivity due to brittleness and poor adhesion, requiring high pressure for compaction which can lead to a decrease in conductivity when binders are added to compensate for strength.
Innovation Solution
Incorporating sulfur in the form of S8 molecules within the argyrodite crystal structure to create a softer and more uniform crystal, improving adhesion and lithium ion conductivity without the need for high pressure or excessive binders, characterized by specific Raman spectroscopy and DSC curve features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a relatively large pressure is applied to improve lithium ion conductivity by sufficiently adhering the powder, then adhesion is improved, but the green compact becomes brittle and requires binders which reduce lithium ion conductivity
Solution Approach 1:
The patent changes the chemical composition parameters of the sulfide solid electrolyte by incorporating S8 molecules and controlling the ratio of fast ion conductor phase to skeleton phase within 90:10 to 50:50 by mass. This compositional parameter change modifies the material's inherent properties to achieve both good adhesion and high lithium ion conductivity without requiring high pressure or excessive binders.
Solution Approach 2:
The patent creates a composite sulfide solid electrolyte material consisting of two phases: a fast ion conductor phase (providing lithium ion conductivity) and a skeleton phase (providing structural stability). This composite structure at the micro-level allows the material to simultaneously exhibit good adhesion properties and high ionic conductivity, resolving the contradiction between strength and reliability.
2Strength
If the addition amount of binder increases to compensate for brittleness, then strength is improved, but the proportion of sulfide solid electrolyte decreases and lithium ion conductivity may decrease
Solution Approach 1:
The sulfide solid electrolyte material serves itself by having intrinsic properties that provide both structural integrity and ionic conductivity. The dual-phase composition enables the material to self-support without requiring external binders, or with minimal binder addition, thus maintaining high lithium ion conductivity while achieving sufficient strength.
3Strength
If high pressure is applied to process the powder into a green compact, then adhesion is improved, but the processing complexity and energy consumption increase
Solution Approach 1:
By changing the compositional parameters to include S8 molecules and optimize the phase ratio, the material's processability is improved. This allows green compacts to be formed at lower pressures with simpler processing equipment and reduced energy consumption, while still achieving the required adhesion and conductivity performance.
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 approach results in a sulfide solid electrolyte with enhanced adhesion and lithium ion conductivity, allowing for the production of a green compact with improved battery characteristics and reduced brittleness, while maintaining a high proportion of sulfide solid electrolyte in the compact.
Implementation Method 1
the sulfide solid electrolyte has a peak in at least one selected from the group consisting of 140 cm−1 to 170 cm−1, 205 cm−1 to 235 cm−1, and 460 cm−1 to 490 cm−1 in a Raman spectrum obtained by Raman spectroscopy measurement
Implementation Method 2
the sulfide solid electrolyte does not have an endothermic peak within a range of 70° C. to 160° C. in a DSC curve obtained by differential scanning calorimetry
Data Source
AI summary
The present invention relates to a sulfide solid electrolyte to be used in a lithium-ion secondary battery, including an argyrodite crystal structure including Li, P, S, and Ha, in which Ha is at least one selected from the group consisting of F, Cl, Br, and I, the sulfide solid electrolyte has a peak in at least one selected from the group consisting of 140 cm−1 to 170 cm−1, 205 cm−1 to 235 cm−1, and 460 cm−1 to 490 cm−1 in a Raman spectrum obtained by Raman spectroscopy measurement, and the sulfide solid electrolyte does not have an endothermic peak within a range of 70° C. to 160° C. in a DSC curve obtained by differential scanning calorimetry.