Method for preparing lithium difluorophosphate

Abstract

The invention relates to the field of lithium battery electrolyte additives and in particular to an economic preparation method suitable for industrially producing lithium difluorophosphate. The method at least comprises the following steps: (1), enabling an oxidized boron compound to react with lithium hexafluorophosphate, to obtain a lithium difluorophosphate mixture; and (2), concentrating thelithium difluorophosphate mixture, adding a poor solvent, crystallizing, and separating to obtain the lithium difluorophosphate.

Description

technical field [0001] The invention relates to the field of lithium battery electrolyte additives, in particular to an economical preparation method of lithium difluorophosphate suitable for industrial production. Background technique [0002] With the technological development and commercialization of lithium-ion batteries, lithium-ion batteries are widely used in consumer electronics, power products, and energy storage products. In the next few years, lithium-ion batteries will become an expanding global industry. At the same time, with the expansion of its application field, the demand for further improvement of battery characteristics is also increasing. As a conductive salt, lithium difluorophosphate can form a film on the electrode interface to improve high and low temperature cycle performance and effectively reduce the amount of lithium hexafluorophosphate used in batteries and batteries. Therefore, in the context of the continuous expansion of the market size of ...

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Problems solved by technology

In addition, published patent WO2012004187A2 proposes a method for producing lithium difluorophosphate, wherein LiHPO 4 Gas-solid reaction occurs with HF at 140°C to form a mixture of lithium difluorophosphate, lithium monofluorophosphate and lithium fluoride, which is difficult to separate; published patent WO2012004188A1 proposes another method for producing lithium difluorophosphate, wherein P 2 o 5 A solid-solid reaction occurs with LiF at 300°C to form a solid solution mixture of lithium difluorophosphate and lithium phosphate. A small amount of lithium difluorophosphate can only be separated after grinding and extraction for a long time; Japanese Patent Laid-Open 2014- 62036 uses LiPF 6 Lithium difluorophosphate is obtained by mixing with LiCl and then passing water vapor. Although this method has cheap raw materials, the reaction is not easy to control, and there are many by-products, which are difficult to purify and are not suitable for large-scale production.

Japanese Patent Special Table 2013-534511 adopts P 4 o 10 The powder reacts with LiF powder. Due to the solid-solid reaction, the resulting mixture is extracted with an organic solvent. This method has high requirements on the reaction conditions, which is not conducive to safe production, energy saving and emission reduction, and the yield is low, the operation is complicated, and it is easy to form by-product

[0004] It can be seen from the above that there are various defects in the existing preparation method, or the process is complicated, the cost is high, it is difficult to industrialize production, or the yield is low, there are many by-products, it is not easy to purify, and the prepared difluorophosphate has low purity, which affects the product performance.