Lithium Titanium Thiophosphate Sintering for Solid Electrolyte Conductivity
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Solution Overview
Problem
The existing methods for preparing lithium titanium thiophosphate LiTi2(PS4)3 do not optimize ionic conductivity, primarily due to large grain boundary resistance, which hinders its performance as a solid electrolyte in all-solid-state battery systems.
Innovation Solution
A method involving mechanical milling or melt-quenching of a mixture of lithium sulfide, phosphorus sulfide, and titanium sulfide to produce an intermediate amorphous sulfide mixture, followed by heat treatment and sintering at specific temperatures (200° C. to 400° C.) to enhance ionic conductivity by reducing grain boundary resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium titanium thiophosphate is prepared using conventional synthesis methods, then the material can be obtained, but the ionic conductivity remains low due to large grain boundary resistance
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature to a specific range (200-400°C) to reduce grain boundary resistance. This temperature parameter modification enables significant improvement in ionic conductivity without compromising material stability, directly resolving the contradiction between obtaining the material and achieving high ionic conductivity.
Solution Approach 2:
The patent employs preliminary action through a compression step before sintering, where the powder is compressed to form a green compact. This preliminary densification prepares the material structure for subsequent sintering, facilitating better grain boundary connection and reducing resistance before the thermal treatment is applied.
2Reliability
If sintering temperature is increased to reduce grain boundary resistance, then ionic conductivity improves, but material stability may be compromised
Solution Approach 1:
The patent precisely defines the sintering temperature parameter range (200-400°C) to achieve optimal balance between ionic conductivity improvement and material stability. This parameter optimization ensures that the thermal energy is sufficient to reduce grain boundary resistance while remaining below temperatures that would cause decomposition or phase changes, thus resolving the contradiction between conductivity enhancement and stability maintenance.
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 method significantly increases the ionic conductivity of LiTi2(PS4)3, with a preferred sintering temperature range of 250° C. to 375° C., resulting in improved connection of polycrystals and reduced resistance, thereby enhancing its performance as a solid electrolyte in all-solid-state batteries.
Implementation Method 1
sintering the lithium titanium thiophosphate obtained as a compressed powder layer in step (b) at a temperature of at least 200° C. and at most 400° C.
Implementation Method 2
subjecting the mixture prepared in step (β) to a heat treatment step at a maximum plateau temperature of at least 350° C. and less than 500° C.
Data Source
AI summary
A method of treatment of a sample of lithium titanium thiophosphate LiTi2(PS4)3 including: (a) providing a solid sample of lithium titanium thiophosphate LiTi2(PS4)3, (b) compressing the lithium titanium thiophosphate sample provided in step (a) to form a compressed powder layer; and (c) sintering the lithium titanium thiophosphate obtained as a compressed powder layer in step (b) at a temperature of at least 200° C. and at most 400° C.