HFSI Purification via Crystallization and Solvent Washing
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Solution Overview
Problem
Existing methods for synthesizing hydrogen bis(fluorosulfonyl)imide (HFSI) result in crude products contaminated with impurities like fluorosulfonic acid, hydrochloric acid, and sulfuric acid, which are difficult to separate and can negatively impact the properties and performance of alkali-metal FSI salts, particularly in lithium-ion batteries.
Innovation Solution
A method involving the use of anhydrous organic solvents under inert conditions to crystallize HFSI while keeping impurities dissolved, allowing for the separation of purified HFSI by temperature control, followed by washing and drying to achieve low impurity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional synthesis methods are used to produce HFSI, then production cost and ease of manufacture are improved, but impurity levels increase and product purity deteriorates
Solution Approach 1:
The patent extracts impurities from crude HFSI by dissolving the crude product in anhydrous organic solvent and selectively crystallizing pure HFSI, leaving impurities dissolved in the mother liquor. This extraction process separates the desired product from contaminants without requiring complex purification equipment.
Solution Approach 2:
The patent changes the temperature parameter to control the crystallization process. By cooling the solution to a temperature where HFSI crystallizes but impurities remain dissolved, the method achieves purification. The temperature is then increased to dissolve the crystals and repeat the process for higher purity.
2Manufacturing precision
If multiple purification steps are implemented to improve purity, then product purity improves, but device complexity and processing time increase
Solution Approach 1:
The patent uses repeated cycles of temperature change to achieve high purity through simple crystallization-dissolution steps. Each cycle involves cooling to crystallize HFSI, filtering, then heating to dissolve and repeat the process. This iterative parameter change achieves purification without adding complex equipment.
Solution Approach 2:
The patent exploits the phase transition of HFSI between solid and dissolved states through controlled temperature changes. By cycling between crystallization (solid formation) and dissolution (solid to liquid), the method purifies HFSI using only phase change and filtration, avoiding complex separation technologies.
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 effectively reduces impurity levels in HFSI to below 1 ppm, improving the purity and performance of alkali-metal FSI salts used in electrolytes for batteries, enhancing stability, solubility, and reducing chloride levels to prevent corrosion.
Implementation Method 1
contacting the crude HFSI with at least one anhydrous organic solvent under inert conditions to create a solution containing the crude HFSI and the one or more target impurities
Implementation Method 2
causing the solution to have a temperature sufficient to cause the HFSI in the solution to crystallize while the one or more target impurities remain dissolved in a mother liquor of the solution
Implementation Method 3
separating the crystallized HFSI from the mother liquor containing the one or more dissolved target impurities
Implementation Method 4
The method further includes washing the crystallized HFSI with at least one anhydrous organic solvent at a temperature below the melting point of the HFSI
Implementation Method 5
drying to achieve low impurity levels
Data Source
AI summary
A method of removing one or more target impurities from crude hydrogen bis(fluorosulfonyl)imide (HFSI) using a crystallization technique. In some embodiments, the method includes contacting the crude HFSI with at least one anhydrous solvent to create a solution. The solution is caused to have a temperature sufficient to cause HFSI in the solution to crystalize while the one or more impurities remain dissolved in the mother liquor of the solution. The crystalized HFSI and the mother liquor containing the one or more impurities are separated to obtained a purified HFSI product. Purified HFSI products are also disclosed, as are systems, such as secondary batteries, incorporating purified HFSI products.