Method for synthesizing phosphorus pentafluoride and preparing lithium hexafluorophosphate by solid phase method

Abstract

The invention discloses a method for synthesizing phosphorus pentafluoride and preparing lithium hexafluorophosphate by a solid phase method, the method comprises the following steps of: (1) drying defluorination slag, mixing the defluorination slag with phosphorus pentoxide according to a certain proportion in a solid phase to react for 1-4 hours, and introducing gas generated by the reaction into an ether absorber for later use; (2) adding pure water into lithium carbonate to prepare a solution, reacting with hydrofluoric acid, centrifugally filtering, washing, and drying in vacuum to obtain a lithium fluoride intermediate product; and (3) adding lithium fluoride and the diethyl ether solution dissolved with phosphorus pentafluoride into a reaction kettle, controlling the reaction temperature and time, transferring the reaction solution into a crystallizer, adding methylbenzene into the crystallizer, crystallizing and separating out lithium hexafluorophosphate, centrifugally filtering, and drying in vacuum to obtain the high-purity lithium hexafluorophosphate product. The phosphorus pentafluoride is synthesized by adopting a solid phase method, the raw material source is wide, the cost is low, the purity of the phosphorus pentafluoride obtained by the reaction is high due to single gas phase component, and in addition, the purity of the obtained lithium hexafluorophosphate product is greater than or equal to 99.95%.

Description

technical field [0001] The invention relates to the field of preparation of lithium ion battery electrolyte salts, in particular to a method for synthesizing high-purity phosphorus pentafluoride and lithium hexafluorophosphate at low cost by a solid-phase method. Background technique [0002] Lithium hexafluorophosphate (LiPF 6 ) is the most important solute in the electrolyte of lithium-ion batteries. It has good ion transfer number and dissociation constant, high electrical conductivity and electrochemical stability, and good oxidation resistance and aluminum foil passivation ability. It can be used with various It is the most widely used commercially used lithium battery solute at present. At present, the most extensive preparation route for industrial production of lithium hexafluorophosphate is LiF+PF 5 →LiPF 6 , FOOTE Mining applied for a patent in the United States in 1970, and the subsequent preparation patents are all process improvements based on this patent, wh...

AI Technical Summary

Problems solved by technology

[0003] The key to the preparation of lithium hexafluorophosphate lies in the phosphorus source (PF 5 ), which is also one of the keys for each production enterprise to reduce costs. The traditional process uses PCl 5 React with excess HF at low temperature, and react the generated mixed gas with HF solution dissolved in LiF to prepare LiPF 6 , PCl 5 The preparation route is 2P+3Cl 2 →2PCl 3 , PCl 3 +Cl 2 →PCl 5 , the production needs to be equipped with chlor-alkali industry and the intermediate product PCl 3 Regulated and expensive to produce

Chinese patent CN101723347B (2009, more than fluoride) announced a low-cost lithium hexafluorophosphate preparation method, reacting phosphoric acid with anhydrous hydrogen fluoride to obtain an aqueous solution of hexafluorophosphoric acid, using oleum to remove the water, and heating the mixed solution to obtain PF 5 Gas, the disadvantage of this process is that the concentration of hexafluorophosphoric acid solution is low, and a large amount of fuming sulfuric acid needs to be added to react the contained water

Chinese patent CN10421369B (Tianci Materials, 2014) uses polyphosphoric acid instead of phosphoric acid to react with anhydrous hydrogen fluoride, which can greatly reduce the amount of oleum used. The disadvantage is that there are many types of gas generated, which need to undergo multi-stage condensation, rectification and purification to obtain High purity PF 5 gas

Images