Lithium Sulfide Powder Purification via Solvent Extraction
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Solution Overview
Problem
Existing methods for synthesizing lithium sulfide for sulfide-based solid electrolytes face challenges such as high cost, environmental issues, and the presence of oxygen-containing impurities, which affect the performance of solid-state batteries.
Innovation Solution
A method involving the mixing of a carbon material and a lithium compound, followed by filtration with a solvent, and addition of sulfur powder, then heat treatment, is used to produce lithium sulfide with controlled oxygen content below 3.5%, ensuring high purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the carbonthermal reduction method is used to produce lithium sulfide, then production cost is reduced and toxic hydrogen sulfide gas is avoided, but oxygen-containing impurities remain in the final product affecting solid electrolyte performance
Solution Approach 1:
The patent extracts and removes oxygen-containing impurities from the lithium sulfide product through a washing process using specific solvents. The impurities are separated from the main product by dissolving them in the solvent and filtering them out, thereby improving the purity of lithium sulfide while maintaining the cost-effective carbonthermal reduction method.
Solution Approach 2:
The patent introduces a washing solvent as an intermediary substance to facilitate the removal of oxygen-containing impurities. The solvent acts as a mediator between the impurities and the final product, enabling selective dissolution and separation of impurities without affecting the main lithium sulfide product.
2Manufacturing precision
If high-purity hydrogen sulfide is reacted with metallic or organic lithium compounds to produce high-purity lithium sulfide, then product purity is improved, but production cost increases and environmental issues arise
Solution Approach 1:
The patent replaces expensive starting materials (high-purity hydrogen sulfide and metallic/organic lithium compounds) with cheaper alternatives (lithium sulfate and carbon). The washing solvent is used as a disposable medium to achieve purification without requiring expensive raw materials, thereby reducing production cost while maintaining product purity.
Solution Approach 2:
The patent changes the chemical parameters of the starting materials from high-cost reagents to low-cost alternatives. By using lithium sulfate and carbon instead of expensive lithium compounds and hydrogen sulfide, the process achieves cost reduction. The washing step then adjusts the purity parameter to meet the required specifications for solid electrolyte production.
3Ease of operation
If the extraction solution is not properly dried after thermal reduction, then processing is simplified, but physical properties of the dried material vary and product quality is compromised
Solution Approach 1:
The patent performs preliminary drying of the extraction solution before the thermal reduction step. By removing moisture in advance, the process ensures consistent physical properties of the dried material during subsequent thermal reduction, thereby maintaining product quality while keeping the overall process simple and manageable.
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 effectively controls oxygen-containing impurities, producing lithium sulfide suitable for high-purity sulfide-based solid electrolytes, enhancing the performance and safety of solid-state batteries.
Implementation Method 1
the carbonthermal reduction method offers advantages in that it does not involve the use of toxic hydrogen sulfide (H 2 S) gas and allows the use of low-cost lithium sulfate (Li 2 SO 4 )
Implementation Method 2
in the solid-phase thermal reduction step, it is necessary to subsequently use a solvent for extraction after calcination
Implementation Method 3
it is necessary to subsequently use a solvent for extraction after calcination. This introduces the need to address issues related to the control of the physical properties of the extraction solution, drying of the extraction solution, calcination, and crystallization
Data Source
Figure 1~2b
Figure 2c~2e
Figure 2f
AI summary
The present invention relates to a lithium sulfide powder and a method for producing the same. The method comprises: a step of mixing a carbon material and a lithium compound to prepare a lithium-carbon compound; a step of filtering a solution obtained by mixing the lithium-carbon compound with a solvent; a step of adding sulfur powder to the filtrate such that the molar ratio of sulfur added to lithium ions is from 0.01 to 0.04; a step of drying the filtrate; and a step of heat-treating the dried material, whereby lithium sulfide having an oxygen content of from 1.0% to less than 3.5% can be produced.