Preparation method of lithium difluorophosphate

Abstract

The invention relates to a preparation method of lithium difluorophosphate, which comprises the steps of sequentially adding a solvent A, lithium hexafluorophosphate and lithium hydroxide into a container, and reacting in a carbon dioxide atmosphere to obtain a reaction solution; filtering the reaction solution, performing vacuum drying to constant weight to obtain a white solid containing lithium difluorophosphate and lithium fluoride, pouring the white solid into a solvent B for dissolving, and filtering to respectively obtain a lithium fluoride precipitate and a filtrate; and carrying out distillation and vacuum drying on the filtrate until the weight is constant so as to obtain a white solid anhydrous lithium difluorophosphate pure product. The method has the characteristics of low cost, high efficiency and easiness in realization of industrial production.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a preparation method of lithium difluorophosphate. Background technique [0002] Lithium-ion battery is a new type of green energy, which is widely used in many fields, such as portable electronic products and electric vehicles, due to its advantages of high working voltage, environmental protection and pollution-free, light weight, and no memory effect. At the same time, with the country's implementation of the goals of "carbon peak" and "carbon neutrality", the new energy automobile industry has been vigorously supported, making the market demand for lithium-ion batteries increasingly large. The Japanese patent "JP-11-67270" mentioned for the first time that lithium difluorophosphate (LiPO 2 f 2 ) can improve the high-temperature cycle performance of the battery, which has since sparked people's interest in LiPO 2 f 2 widespread attention. LiPO 2 f 2 There ...

AI Technical Summary

Problems solved by technology

[0003] There are many traditional methods for synthesizing lithium difluorophosphate, for example: (1) LiPO is prepared by reacting lithium oxide, lithium hydroxide (LiOH) with difluorophosphoric anhydride 2 f 2 , with LiOH as raw material, water is generated during the preparation process, so that the prepared LiPO 2 f 2 There is the possibility of hydrolysis; (2) In order to solve LiPO 2 f 2 For the problem of hydrolysis, Japan Stella Chemicals uses phosphorus oxyhalides, phosphorus oxyacids (anhydrides) and hydrogen fluoride to prepare difluorophosphoric acid, and lithium hexafluorophosphate (LiPF 6 ) as a lithium source or moisture absorbent, but halides may introduce halide ion impurities, and hydrogen fluoride is highly corrosive; (3) patent CN2020114408007 discloses the use of lithium phosphate (Li 2 CO 3 ), lithium dihydrogen phosphate and phosphorus pentafluoride as raw materials to prepare LiPO 2 f 2 method, but the raw material cost of this method is too high to meet the needs of industrialization; (4) Patent CN2017111369615 discloses the use of LiPF 6 and Li 2 CO 3 Preparation of LiPO as raw material and ultrapure water as catalyst 2 f 2 method, but the method has many by-products and the reaction is not easy to control; (5) patent CN2017100325308 discloses the use of LiPF 6 Preparation of LiPO with silane boron (or phosphate) ester as raw material 2 f 2 method, but the reaction conditions are harsh and the raw materials are expensive, resulting in high production costs; (6) patent CN2020115431439 discloses a gas-liquid-solid three-phase preparation of LiPO 2 f 2 method using silicon oxide, LiF and POF 3 as raw material, but the raw material cost is high, and POF 3 Afraid of water, pungent smell and strong corrosion, not conducive to industrial production

[0004] Although the above methods have higher yields, these methods are limited by the high price of raw materials, LiPO 2 f 2 Due to limitations such as rising production costs, difficult purification, and many by-products, it is difficult to achieve industrial-scale production

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