Preparation of LiPF6 using ClF3 below room temperature

A reaction among LiF, P (red phosphorous), and ClF3 was conducted to prepare LiPF6 at −20 to 100 °C. First, P reacts with ClF3 to form PF5. Then PF5 reacts with LiF to form LiPF6. The reaction preparing LiPF6 from LiF, P, and ClF3 can take place at less than 0 °C, although the reaction using F2 instead of ClF3 did not proceed well at such a lower reaction temperature. The LiPF6 preparation reaction can be promoted by increasing the reaction temperature. However, if the reaction temperature increases, some side reaction and/or decomposition reaction take place. The optimal conditions to obtain highly pure LiPF6 in this study were 0 °C reaction temperature and 5 h reaction time for the composition of LiF:P:ClF3 = 1:1:2 (mol) as the starting mixture.