Preparation method of high purity difluorophosphate

Abstract

The invention discloses a preparation method of high purity difluorophosphate. The preparation method comprises the following steps: dissolving meta-phosphoric acid in alcohol, then introducing hydrogen fluoride into the alcohol to carry out fluorination reactions to obtain monofluorophosphoric acid, reacting monofluorophosphoric acid with phosphorus oxyfluoride gas to obtain difluorophosphoric acid, then reacting difluorophosphoric acid with alkali metals or alkali-earth metal halides, and separating the reaction products to obtain high purity difluorophosphate. The preparation method has the advantages that the raw materials are cheap and easily-available, a homogenous reaction technology is adopted, thus the reaction speed is greatly increased; during the reaction process, the excess raw materials and solvents can be separated, recovered, and reused through fractionation, thus the amount of generated wastes is reduced; and during the whole process, no water is generated, so the product will not be hydrolyzed. The high purity difluorophosphate can be used to produce electronic chemicals.

Description

technical field [0001] The invention relates to the technical field of chemical synthesis, in particular to a method for preparing high-purity difluorophosphate. Background technique [0002] The lithium-ion battery industry is currently one of the industries with the potential for rapid growth that has attracted much attention, especially in emerging applications such as power and energy storage. The expansion of the market urgently needs the improvement of battery technology, and the development of new electrolytes is the key link. A large number of electrolyte additives with excellent characteristics have been developed and used, and fluorine-containing phosphate is one of them. [0003] In Sanyo Electric's patent (JPH1167270), the use of Li 2 PO 3 F and LiPO 2 f 2 As a film-forming additive, it significantly improves the high-temperature storage performance of lithium-ion batteries. In Sony's patent (CN102983359), LiPO 2 f 2 The combined use of methylene cyclic car...

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Problems solved by technology

[0004] There are many reports on the synthesis method of difluorophosphate, and Vast et al. (VastP, etal.Journaloffluorinechemistry, 1988,38(3):297-302) have reported that difluorophosphoric anhydride and lithium oxide or lithium hydroxide are used to produce difluorophosphate. The method of fluorophosphate; Japanese patent JP2012051752 uses difluorophosphoric acid to react with metal chlorides, and crystallizes in difluorophosphoric acid to obtain difluorophosphate. Japanese patent JP2010155773 discloses the use of halides such as alkali metals and difluorophosphoric acid in A method for producing lithium difluorophosphate by reacting in the presence of hexafluorophosphate; Japanese patent JP2010155774 uses phosphorus oxyacids or anhydrides to react with lithium hexafluorophosphate in the presence of hydrogen fluoride to prepare difluorophosphate; Japanese patent JP2005219994 uses lithium hexafluorophosphate and carbon dioxide Silicon is synthesized by reacting in carbonate / carboxylate solution, and the by-product is silicon tetrafluoride. In Japanese patent JP2005053727 and Chinese patent CN102064345, lithium hexafluorophosphate and lithium metaborate, tetrafluoride are formed in carbonate / carboxylate solution. Lithium fluoroborate or hexamethyldisiloxane is prepared by reacting; in Chinese patent CN102985361, phosphorus pentoxide and lithium fluoride are used to synthesize lithium difluorophosphate in solid phase at a high temperature of 350°C, and a large amount of phosphoric acid is produced as a by-product of the reaction Lithium, raw material utilization efficiency is not high

[0005] Using difluorophosphoric anhydride for synthesis is not suitable for industrialization because difluorophosphoric anhydride is expensive and difficult to obtain high-purity raw materials; using difluorophosphoric acid for synthesis also has the problem of lack of industrial raw material supply, and difluorophosphoric acid has fluorination , hydrolysis and other reversible transformations, the existence of trace moisture or hydrogen fluoride will make the product impure; the synthesis scheme using lithium hexafluorophosphate, on the one hand, due to the high price of lithium hexafluorophosphate, increases the manufacturing cost, on the other hand, most schemes have a long reaction time , low efficiency, a large amount of by-products and three wastes that need to be treated, and more importantly, there is water in the system, which causes the fluorination and hydrolysis balance of various fluorine-containing phosphates in the whole system, which makes the product impurity content high, and further purification is difficult

The high-temperature solid-phase synthesis of phosphorus pentoxide and lithium fluoride produces a large amount of lithium phosphate by-product, the utilization efficiency of raw materials is not high, and there are also very complicated separation and purification problems

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