Bis(Fluorosulfonyl)Imide Salt Synthesis With Low-TOC Fluorination
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Solution Overview
Problem
Current methods for producing bis(fluorosulfonyl)imide and its salts, such as LiFSI, face challenges in achieving high purity and economic feasibility at an industrial scale due to issues like excessive solvent use, by-product management, and impurity contamination, particularly in battery electrolyte applications.
Innovation Solution
A method involving the reaction of bis(chlorosulfonyl)imide with an onium halide in the absence or minimal presence of solvent to produce onium salts of bis(chlorosulfonyl)imide, followed by reaction with onium fluoride to obtain onium salts of bis(fluorosulfonyl)imide, and subsequently with an alkali metal salt to produce alkali metal salts of bis(fluorosulfonyl)imide, reducing solvent usage and by-product waste while maintaining high purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorination reaction is conducted in organic solvent, then reaction proceeds smoothly, but heat generated degrades the solvent and increases TOC content
Solution Approach 1:
The invention changes the physical state parameter of the reaction medium from liquid organic solvent to molten salt state. By conducting the fluorination reaction in molten HFSO3N(SO2F) at temperatures above its melting point (100-150°C), the process eliminates solvent degradation and TOC generation while maintaining reaction efficiency through the reactive medium's high temperature state.
Solution Approach 2:
The invention replaces expensive organic solvents that require purification and disposal with a reusable molten salt system. The molten HFSO3N(SO2F) acts as both reactant and reaction medium, eliminating the need for separate solvent recovery and purification steps, thereby reducing operational costs and complexity.
2Manufacturing precision
If significant amount of NH4F(HF)p is used for fluorination, then chlorosulfonlyimide compound is fully fluorinated, but process becomes not cost-effective
Solution Approach 1:
The invention changes the chemical form of the fluorinating agent from NH4F(HF)p to HFSO3N(SO2F). This parameter change in reagent identity provides superior fluorinating capability with lower stoichiometric requirements, improving both conversion efficiency and cost-effectiveness simultaneously.
Solution Approach 2:
The invention employs a composite molecular structure in HFSO3N(SO2F) that combines fluorinating functionality with sulfonimide backbone stability. This composite structure allows the reagent to act as both fluorinating agent and potential product precursor, reducing waste and improving atom economy.
3Productivity
If chlorosulfonlyimide compound is reacted with fluorinating agent to produce NH4FSI, then fluorosulfonylimide salt is obtained, but high amounts of solid halogenated salt by-products are generated
Solution Approach 1:
The invention converts the harmful halogenated by-products into beneficial reusable materials. The HCl gas generated during fluorination is captured and converted to HFSO3N(SO2F) through reaction with SO3 and additional reagents, closing the material cycle and eliminating waste disposal needs.
Solution Approach 2:
Instead of discarding the HCl by-product as waste, the invention implements a recovery system where HCl is captured, converted to valuable HFSO3N(SO2F) reagent, and reused in the fluorination process. This circular approach eliminates waste and reduces raw material consumption.
4Manufacturing precision
If additional treatment steps are performed to remove by-products and achieve required purity, then product purity is improved, but production cost and time increase
Solution Approach 1:
The invention performs preliminary purification by conducting the fluorination reaction directly in molten HFSO3N(SO2F) without organic solvents. This preliminary action prevents solvent-related impurities and simplifies downstream processing, as the reaction medium itself is the desired product or can be easily separated.
Solution Approach 2:
The invention extracts the problematic organic solvent component from the reaction system entirely, replacing it with molten inorganic salt medium. This extraction of the harmful element (organic solvent) eliminates the need for complex solvent removal and purification steps while maintaining reaction effectiveness.
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 approach results in high-purity onium and alkali metal salts of bis(fluorosulfonyl)imide with reduced TOC impurities, lower production costs, and the ability to recycle by-products, enhancing the process's economic and environmental sustainability.
Implementation Method 1
reacting a bis(chlorosulfonyl)imide or a salt thereof with an onium halide other than an onium fluoride to produce an onium salt of bis(chlorosulfonyl)imide
Implementation Method 2
reacting the onium salt of CSI with an onium fluoride to produce an onium salt of FSI
Implementation Method 3
reacting the onium salt of FSI with an alkali metal salt to obtain an alkali metal salt of FSI
Data Source
AI summary
The invention relates to a new method for producing an onium salt of bis(fluorosulfonyl)imide and an alkali metal salt of bis(fluorosulfonyl)imide of high purities, as industrial scale, and with a reasonable cost when compared to the other available methods. Said method comprises the steps of reacting bis(chlorosulfonyl)imide or salts thereof with an onium halide other than an onium fluoride to produce an onium salt of bis(chlorosulfonyl)imide, reacting the onium salt of bis(chlorosulfonyl)imide with an onium fluoride to produce an onium salt of bis(fluorosulfonyl)imide; the onium salt of bis(fluorosulfonyl)imide may be further reacted with an alkali metal salt to obtain an alkali metal salt of bis(fluorosulfonyl)imide.