Lithium Bis(fluorosulfonyl)imide Preparation via Crown Ether Catalysis

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Solution Overview

Problem

Existing methods for preparing lithium bis(fluorosulfonyl)imide result in products with high impurity levels, such as chlorofluorosulfonyl imide and fluorosulfonyl imide, making it difficult to obtain a solid salt with high yield and purity, which hinders industrial implementation.

Innovation Solution

Direct fluorine-chlorine exchange reaction between lithium bis(chlorosulfonyl)imide and an alkali metal fluoride in the presence of a crown ether phase transfer catalyst and a suitable solvent, such as saturated alkyl or fluoroalkyl carbonate, to produce lithium bis(fluorosulfonyl)imide with low impurity levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional methods using bis(chlorosulfonyl)imide and fluorosulfonic acid are used, then the reaction can proceed, but the product contains high levels of impurities such as chlorofluorosulfonyl imide and fluorosulfonyl imide

Engineering Contradiction:

Improveproduct purityVSAvoidimpurity content

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The invention extracts and removes harmful impurities (chlorofluorosulfonyl imide, fluorosulfonyl imide) from the product through a multi-step purification process including filtration, extraction with water and organic solvents, and recrystallization, achieving product purity above 99.5%

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the reaction parameters by using a different solvent system (acetonitrile instead of nitromethane), controlling reaction temperature (0-25°C), and adjusting stoichiometry to minimize impurity formation and facilitate their removal

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If conventional purification methods are used, then some impurities can be removed, but the separation of acid esters and potassium ions is difficult and time-consuming

Engineering Contradiction:

Improveproduct purityVSAvoidpurification time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The invention uses an intermediary extraction system comprising water, organic solvent (dichloromethane or ethyl acetate), and activated carbon that efficiently mediates the separation of impurities including acid esters and potassium ions from the product in a single integrated purification step

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The purification process is segmented into distinct stages: filtration through activated carbon, extraction with water and organic solvent, and recrystallization, allowing each impurity type to be removed in its optimal condition

Inventive Principle:

Principle #1Segmentation

3Productivity

If the reaction is carried out in nitromethane as used in US7253317, then the reaction can proceed, but the product contains difficult-to-separate impurities and solid salt is difficult to obtain

Engineering Contradiction:

ImproveyieldVSAvoidproduct isolation difficulty

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The invention changes the solvent parameter from nitromethane to acetonitrile, which enables better solubility control and product crystallization, making it easier to obtain solid salt product with high yield and purity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention utilizes phase transition by controlling the reaction and crystallization process in acetonitrile to precipitate the product as a solid salt, facilitating easy separation and purification

Inventive Principle:

Principle #36Phase transitions

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 yields lithium bis(fluorosulfonyl)imide with impurity levels below 10ppm, ensuring high purity and stability, facilitating industrial production and meeting electronic application requirements.

Implementation Method 1

reacting lithium bis(chlorosulfonyl)imide with an alkali metal fluoride selected from lithium fluoride, potassium fluoride, sodium fluoride or mixtures thereof used as a fluorinating agent in a solvent selected from saturated alkyl carbonate and/or saturated fluoroalkyl carbonate in the presence of a crown ether phase transfer catalyst adaptive to the alkali metal fluoride

Methodology Applied

Scientific EffectPhase transfer catalysis: Catalysis

Data Source

PatentEP2894146B1Method for preparing bis(fluorosulfonyl)imide

Publication Date: 2018.08.22 ZHANGJIAGANG HUASHENG CHEM CO LTD

Figure 1

AI summary

The invention relates to a method of preparing lithium bis(fluorosulfonyl)imide, comprising: reacting lithium bis(chlorosulfonyl)imide with an alkali metal fluoride used as a fluorinating agent in a solvent of saturated alkyl carbonate and/or saturated fluoroalkyl carbonate in the presence of a crownether phase transfer catalyst adaptive to the alkali metal fluoride to obtain lithium bis(fluorosulfonyl)imide. The method of preparing lithium bis(fluorosulfonyl)imide according to the invention possesses a simple process route, and industrial manufacture can be realized easily.