On the thermal stability of LiPF6

The results of a comprehensive study of the thermal stability of the salt LiPF6, using both accelerating rate (ARC) and differential scanning (DSC) calorimetry, are presented. Pressure monitoring during ARC experiments pen-nits also the study of endothermic processes. The origins of apparently inconsistent results and conflicting interpretations in previous reports in the literature are explicated. In a confined volume, LiPF6(S) melts reversibly at 467 K with a heat of melting of 2.0 +/- 0.2 kJ mol(-1). Reversible decomposition to PF5(g) and LiF(s) commences with melting, but the autogenic development of PF5(g) pressure makes the temperature profile of decomposition a function of volume and sample size. The heat of this reaction at constant volume, Delta U-r, as determined by a variety of methods is in the range 60 5 U mol-1, and is approximately temperature independent in range 490-580 K. (C) 2005 Elsevier B.V. All rights reserved.