LixMn2O4 spinels with x = 0.1, 1.0 and 2.0 were examined by Fourier transform infrared spectroscopy at temperatures ranging from -150 to 250 degrees C. The occurrence of a reversible phase transition near 10 degrees C in LiMn2O4 was confirmed. The thermal decomposition of Li0.1Mn2O4 to beta-MnO2 was studied as a function of time and temperature. The instability of this material in its charged state raises some concern about its viability in rechargeable lithium cells.