Li3PS4 Solid Electrolyte Synthesis via Excess Li2S Precipitation
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Solution Overview
Problem
The production of Li3PS4 solid electrolytes for all-solid-state lithium ion secondary batteries is hindered by the generation of by-products during the synthesis process, which affects the battery's charging and discharging performance.
Innovation Solution
A method involving a solution-making step where Li2S and P2S5 are mixed in an organic solvent at a specific molar ratio, followed by a precipitation step with further addition of Li2S, and subsequent drying at 120°C or higher to produce β-Li3PS4 with minimal by-products, using an ether-based solvent like tetrahydrofuran under an inert gas atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Li2S and P2S5 are mixed in THF to precipitate Li3PS4.3THF crystal, then the synthesis process is convenient and fast, but by-products are generated that yellow the reaction solution and prevent normal battery charging and discharging
Solution Approach 1:
The patent changes the molar ratio parameter of Li2S to P2S5 from the conventional 1:1 to 3:1 (excess Li2S), which fundamentally alters the reaction pathway and prevents by-product formation while maintaining the convenience of the THF-based synthesis method
Solution Approach 2:
The patent performs preliminary purification by filtering the reaction mixture to remove excess Li2S particles before drying, ensuring that only pure Li3PS4 product remains without by-products that would interfere with battery performance
2Object-affected harmful factors
If the vitrification treatment is performed in two stages to obtain Li3PS4 with ortho composition, then the amount of hydrogen sulfide generated is very small, but the process becomes complicated
Solution Approach 1:
The patent performs the composition adjustment in advance during the synthesis stage by using excess Li2S, so that the product is obtained directly in the desired ortho composition without requiring subsequent two-stage vitrification treatment
Solution Approach 2:
The patent extracts the composition control step from the post-synthesis vitrification process and integrates it into the synthesis stage, eliminating the need for complex multi-stage treatment
3Manufacturing precision
If Li2S is added in excess to achieve the desired molar ratio, then by-products are suppressed, but the precipitation process requires careful control to maintain homogeneity
Solution Approach 1:
The patent performs preliminary mixing of Li2S and P2S5 in THF to form a homogeneous solution before adding excess Li2S, ensuring uniform distribution and preventing localized by-product formation
Solution Approach 2:
The patent uses THF as an intermediary solvent that facilitates homogeneous mixing and controlled precipitation, allowing excess Li2S to be added without creating heterogeneity or by-products
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 method enables the production of Li3PS4 with significantly reduced by-products, facilitating mass production and ensuring normal charging and discharging performance in all-solid-state batteries.
Implementation Method 1
a homogenous solution is prepared by mixing Li2S and P2S5 into an organic solvent
Implementation Method 2
Li2S is further added to and mixed in the homogenous solution to form a precipitate
Implementation Method 3
the drying temperature in the drying step is 120° C. or higher, and wherein said Li3PS4 is β-Li3PS4
Data Source
AI summary
The present invention can provide a production method for a solid electrolyte having Li3PS4, said method characterized by including: a solution-making step in which a homogenous solution is prepared by mixing Li2S and P2S5 into an organic solvent; and a precipitation step in which further Li2S is added to and mixed in the homogenous solution and a precipitate is formed. Preferably, the embodiment either has a molar ratio (Li2S/P2S5) between the Li2S and the P2S5 in the solution-making step of 1.0-1.85 or has further Li2S added to the homogenous solution in the precipitation step such that the molar ratio becomes Li2S/P7S5=2.7-3.3.