An in-situ, high-energy X-ray diffraction study of the thermal stability of delithiated LiVPO4F

Differential scanning calorimetry (DSC) and in-situ high-energy X-ray diffraction (HEXRD) techniques were used to investigate the high-temperature reactions of a cathode containing Li1-xVPO4F with materials found in a lithium-ion cell, such as graphite additive in the cathode and the electrolyte. The DSC results indicate that the energy released during the reaction of the cathode containing Li1-xVPO4F with the electrolyte was about 1/3 of that released during a similar reaction of the delithiated, layered cathode containing Li-1.1[Ni1/3Mn1/3Co1/3](0.9)O-2. The in-situ HEXRD results provide evidence that the delithiated material, Li1-xVPO4F, reacts with protons and/or lithium ions found in the reaction mixture at elevated temperature, producing an LiVPO4F-like compound. This reaction is the most likely cause for the low energy release during heating, that is, the LiVPO4F-like material appears to be thermally stable at temperatures up to 400 degrees C in the presence of LiPF6. (C) 2014 Elsevier B.V. All rights reserved.