Method for preparing high purity lithium hexafluorophosphate

Abstract

The invention discloses a lithium hexafluorophosphate preparation method, which comprises the following steps: anhydrous acetonitrile is put into a sealed pressure heating furnace, simultaneously solid high-pure nano lithium fluoride is added into the furnace, and after dried inert gas is adopted to drive air out from the furnace a suspension is formed under sealed stirring condition; compressed phosphorus pentafluoride gas is introduced in and the lithium hexafluorophosphate is synthesized continually under the sealed stirring condition. The product prepared by the method has high purification, the content of LiPF<6> is greater than 99.9 percent, the water content is less than 10ppm, the content of HF is less than 50ppm and the content of total impurity metal is less than 50ppm; moreover, the technique is simple, the preparation process is environment-friendly, thus having extremely high industrial popularization value.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to the preparation of electrolyte lithium salts. Background technique [0002] Lithium hexafluorophosphate (LiPF 6 ) is the most widely used electrolyte lithium salt in commercial lithium-ion batteries. Its main advantages are: (1) it can form a proper SEI film on the electrode, especially on the carbon negative electrode; (2) it can effectively passivate the positive current collector to prevent its dissolution; (3) it has a wide Electrochemical stability window; (4) appropriate solubility and high conductivity in various non-aqueous solvents; (5) relatively good environmental friendliness. [0003] At present, the global demand for lithium hexafluorophosphate has reached 1,500 tons, and the supply of three Japanese companies, Stella, Morita, and Kanto, which are capable of providing lithium hexafluorophosphate on a large scale in the world, has far failed to keep up with the...

AI Technical Summary

Problems solved by technology

But the biggest disadvantage of this process is that HF ​​is complexed with LiPF 6 The form of HF remains in the product, and the general method is extremely difficult to reduce the HF content in the product to less than 10ppm, because the residual HF will corrode the battery material, thus affecting the battery electrical performance; in addition, this process will affect the anti-corrosion measures and materials of the equipment The requirements and production safety measures are high; and the process is a cryogenic process, which consumes a lot of energy

These series of reasons have directly led to the high requirements on production equipment for the preparation of lithium hexafluorophosphate by the HF solvent method, which makes the production cost high.