A kind of preparation method of bisfluorosulfonimide lithium salt

Abstract

The invention relates to the field of chemical synthesizing, in particular to a preparation method of imidodisulfuryl fluoride lithium salt. The preparation method includes the steps of firstly, allowing chlorosulfonic acid and chlorosulfonyl isocyanate to react in the presence of catalyst to obtain dichlorosulfimide; secondly, allowing dichlorosulfimide and hydrogen fluoride to react in the presence of catalyst to obtain imidodisulfuryl fluoride; thirdly, allowing imidodisulfuryl fluoride to react with compound containing lithium to obtain the imidodisulfuryl fluoride lithium salt. The preparation method has the advantages that the chlorosulfonic acid and chlorosulfonyl isocyanate are used as the raw materials in the first-step reaction, the generation of waste gases such as SO2 and HCl is avoided, and environment protection requirements are satisfied.

Description

technical field [0001] The invention relates to the field of chemical synthesis, in particular to a preparation method of lithium bisfluorosulfonyl imide. Background technique [0002] Lithium-ion battery, because of its high working voltage, small size, light weight, high energy, no memory effect, no pollution, small self-discharge, and long cycle life, is an important type of secondary battery and is widely used in various Energy storage unit for similar electronic equipment. Lithium bisfluorosulfonyl imide, referred to as LiFSI, is an electrolyte salt used in lithium-ion secondary batteries. It is different from the widely used electrolyte salt LiPF 6 Compared with the high solubility and conductivity in the solvent, it has a wider working temperature range and better stability, and more importantly, it has a large specific energy density, which can effectively improve the discharge load characteristics at low temperatures, and To maintain the capacity retention rate af...

AI Technical Summary

Problems solved by technology

However, the product is easily decomposed when heated in the presence of water or under high temperature conditions, and other metal ions introduced in the conventional production process will also adversely affect its performance

In order to meet the requirements for the use of electrolytes, LiFSI has strict restrictions on indicators such as moisture, metal ions, and free acids. However, there is currently no effective purification method. Once impurities are introduced, it is difficult to achieve the above requirements through purification. The production process avoids the introduction of water, acid and other metal ions to control product quality

[0004] Most of the synthesis methods of LiFSI are to synthesize bischlorosulfonimide (HClSI for short), and then react with MFn (M is Group 11-15, elements of period 4-6) to prepare the corresponding metal or organic base The salt intermediate of bisfluorosulfonimide, and then with LiOH or Li 2 CO 3 Carry out cation exchange reaction to make LiFSI, such as patents US2013331609, US2012041233, EP2415757, US2011034716, the shortcoming of these methods is that it is difficult to continue after the exchange reaction reaches a balance, so that the reaction is incomplete and the conversion rate is low; and the unreacted The intermediate MSFI (M refers to metal cation, organic base cation) has similar properties to LiSFI, and it is difficult to completely separate it, resulting in the low quality of LiFSI, which cannot be directly applied to battery electrolytes

[0005] When U.S. Patent US2004097757 uses HClSI to directly react with LiF to prepare LiFSI, a large amount of corrosive tail gas HF will be produced. The free acid HF remaining in the product will be detrimental to the performance of LiFSI, and tail gas absorption will also increase the difficulty of industrial operation; at the same time, excessive LiF and LiFSI are not easy to separate, resulting in low purity of the final product LiFSI

[0006] Although it has also been reported that with purified potassium bisfluorosulfonimide (KFSI) and LiClO 4 LiFSI is prepared by metal exchange, but the potassium ions in the product are often high, which is difficult to remove by conventional purification methods, which affects its practical application, and LiClO 4 and the resulting KClO 4 , there is a certain risk of explosion (Electrochimical Acta, 2012, 66, PP.320-324, Polyhedron, 2006, 25, PP. 1292-1298, CN101747242, CN101747243, CN101654229)

In addition, since LiClO 4 Generally, a slight excess is required to participate in the reaction, but due to its strong hygroscopicity, the final product contains a small amount of LiClO 4 Cannot be removed, so that the purity of the final product LiFSI cannot be guaranteed

[0007] US8377406 discloses the method that bisfluorosulfonimide (HFSI) directly reacts with Lithium Carbonate to prepare LiFSI in aqueous solution, but this method also has obvious deficiencies, when HFSI is dissolved in water, it exothermic violently, thereby causes the decomposition of HFSI; The patent adopts the method of preparing HFSI aqueous solution at ultra-low temperature (-78°C) to solve the technical problem of violent heat release when HFSI is dissolved in water, but this method increases a lot of energy consumption, and more importantly, LiFSI has very good water solubility property, and it is easy to decompose when heated in the water system, and the extraction efficiency is very low, so it is not suitable for industrial production

[0008] The production process of LiFSI mentioned above has high requirements on reaction equipment, difficult operation, and the problem that LiFSI is in contact with water, free acid, and other metal ions, which makes LiFSI unable to realize industrial application.

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