Preparation Of Lithium Hexafluorophosphate And Investigate On Its Acetonitrile Complex

Electrolyte lithium as an important part of lithium ion battery has many kinds, LiPF6is one of them with the best comprehensive performance. HF solvent method is often used to prepare LiPFf, in industry, which is demanding the production environment, demands the needed equipment with strong corrosion resistance and has certain security hidden danger. At present, the organic solvent method, as a substitute for HF solvent method, is used to prepare LiPF6, which can reduce the security hidden danger, at the same time can proceed under milder conditions and is a kind of preparation method with good application prospect. In view of this, aiming to prepare the LiPF6and investigate the intermediate product Li(CH3CN)PF6, this paper has carried out the following research work:(1) LiPF6was prepared by using one-step method with hydrofluoric acid (HF) gas, phosphorus pentachloride (PC15) and lithium fluoride (LiF) solid as raw material, and acetonitrile as the solvent. Research results show that characteristic absorption peaks of the PF6, in the reaction filtrate are found by fourier transform infrared spectrometer (FT-IR). X-ray diffraction (XRD) test shows that the main characteristic peaks of product are consistent with standard PDF card of LiPF6, determine the main components in solid samples LiPF6. It indicates that the main component of solid samples is LiPF6. According to the results of elemental analysis, the purity and yield of prepared LiPF6are, respectively,77.0%and50.5%by calculating.(2) LiPF6was prepared by using two-step method with hydrofluoric acid (HF) gas, phosphorus pentachloride (PC15) and lithium fluoride (LiF) solid as raw material, and acetonitrile as the solvent. Research results show that characteristic absorption peaks of the PF6-in the reaction filtrate are found by fourier transform infrared spectrometer (FT-IR). X-ray diffraction (XRD) test shows that the main characteristic peaks of the final product are also consistent with standard card of LiPF6, determine the main components in solid samples LiPF6. It indicates that the main component of solid samples is LiPF6. According to the results of elemental analysis, the purity and yield of prepared LiPF6are, respectively,96.3%and94.5%by calculating. Therefore, Two-step method of preparation LiPF6is more superior than one-step method.(3) Li(CH3CN)4PF6was prepared with CH3CN and LiPF6as raw material. Research results show that Li(CF3CN)4PF6has the same characteristic absorption peaks of CH3CN and LiFP6. Thermogravimetric tests show that thermal stability of Li(CFI3CN)4PF6is better than LiPF6and decomposition temperature of Li(CH3CN)4PF6, is range from44.5℃to243.9℃. Elemental analysis tests show that the content of LiPF6, CH3CN and impurity is47.49%,52.49%and0.019%, separately. The best crystallization temperature of Li(CH3CN)4PF6is from-20℃to-30℃. Depressurization method is used to remove the acetonitrile in Li(CH3CN)4PF6and optimum parameters is temperature at20℃and pressure in-0.1MPa.