Study on thermal decomposition of lithium hexafluorophosphate by TG-FT-IR coupling method

Using TG-FT-IR coupling method, direct evidences of the decomposition process of lithium hexafluorophosphate had been obtained. Studies showed that LiPF₆ is stable under normal temperature when the content of water is very low. When heated, LiPF₆ would react with the trace water in the air. HF and OPF₃ would be released in the same time which could be detected from the FT-IR spectra collected in situ. The peak temperature of the decomposition of LiPF₆ varied from 192.93 °C (average heating rate 2.0 °C min^-1) to 223.83 °C (average heating rate 20.0 °C min^-1). Based on the on-line FT-IR spectra, the characteristic absorption bands of PF₆^- in the decomposed substances were detected for the first time which might come from the reaction of trace HF with PF₅.