LiFSI Purification Using Anhydrous Solvent Exchange
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Solution Overview
Problem
Existing methods for producing lithium bis(fluorosulfonyl)imide (LiFSI) often result in crude products containing reactive solvents and impurities, which are challenging to remove and can react with lithium metal in batteries, leading to performance issues and reduced cycle life.
Innovation Solution
A method involving the use of anhydrous organic solvents to replace reactive solvents and remove impurities from LiFSI, including a multi-pass process to achieve low levels of reactive solvents and impurities, ensuring stability and purity for use in lithium-ion and lithium-metal batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional synthesis methods are used to produce LiFSI, then production cost and ease of manufacture are improved, but the product contains reactive solvents and impurities that reduce battery reliability and cycle life
Solution Approach 1:
The patent applies extraction by contacting crude LiFSI with anhydrous organic solvents (such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate) that selectively dissolve reactive solvents (alcohols, water) and impurities while leaving purified LiFSI behind. The reactive solvents and impurities are removed through filtration and evaporation, achieving high purity LiFSI suitable for lithium-metal batteries without compromising manufacturing feasibility
Solution Approach 2:
The patent uses anhydrous organic solvents as intermediary substances to facilitate the removal of reactive solvents and impurities. These intermediary solvents temporarily interact with the crude LiFSI mixture, selectively solvating harmful components, and are then easily removed through evaporation, leaving behind purified LiFSI with enhanced battery reliability
2Duration of action of stationary object
If multiple purification steps are implemented to remove reactive solvents, then battery cycle life and stability are improved, but process complexity and time consumption increase
Solution Approach 1:
The patent combines multiple purification objectives (removal of water, alcohols, and synthesis impurities) into a single integrated purification step using anhydrous organic solvents. This unified approach simultaneously addresses multiple contaminants that would otherwise require separate treatment steps, reducing process complexity while achieving the high purity necessary for extended battery cycle life
Solution Approach 2:
The patent changes the solvent parameter from reactive solvents (water, alcohols) to non-reactive anhydrous organic solvents with specific solubility characteristics. This parameter change enables selective dissolution of impurities while maintaining LiFSI stability, achieving thorough purification in fewer steps and reducing overall process complexity
3Productivity
If reactive solvents are used to remove synthesis impurities, then manufacturing efficiency is improved, but battery performance and longevity deteriorate due to reactions with lithium metal
Solution Approach 1:
The patent creates an inert purification environment by using anhydrous organic solvents that do not react with lithium metal. These inert solvents effectively remove synthesis impurities from crude LiFSI without introducing reactive components that would compromise battery performance, maintaining both manufacturing efficiency and battery reliability
Solution Approach 2:
The patent employs inexpensive anhydrous organic solvents (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate) as disposable purification agents. These solvents perform their purification function efficiently and are then easily removed through evaporation, leaving no harmful residues that would affect battery longevity, thus maintaining both productivity and reliability
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 process effectively reduces reactive solvent levels and impurities in LiFSI, enhancing the stability and cycle performance of lithium-based batteries by preventing reactions with lithium metal, thereby improving battery performance and longevity.
Implementation Method 1
contacting the crude lithium salt with at least one first anhydrous organic solvent under an inert condition to create a solution containing the crude lithium salt and the one or more reactive solvents
Implementation Method 2
subjecting the solution to a vacuum so as to remove the at least one first anhydrous organic solvent and at least a portion of the one or more reactive solvents to obtain a solid mass
Implementation Method 3
treating the solid mass with at least one second anhydrous organic solvent in which the lithium salt is insoluble so as to remove at least a portion of any coordinated or solvated portion of the at least one first anhydrous organic solvent remining in the solid mass
Data Source
AI summary
Methods for making high-purity LiFSI salts and intermediate products using one, the other, or both of a reactive-solvent removal/replacement method and an LiFSI purification method. In some embodiments, the reactive-solvent removal/replacement method includes using non-reactive anhydrous organic solvents to remove and/or replace one or more reactive solvents in a crude LiFSI. In some embodiments, the LiFSI purification method includes using anhydrous organic solvents to remove impurities, such as synthesis impurities, from a crude LiFSI. In some embodiments, crude LiFSI can be made using an aqueous-based neutralization process. LiFSI salts and products made using methods of the disclosure are also described, as are uses of such salts and products and electrochemical devices that include such salts and products.