The thermal stability of pristine and electrochemically delithiated LiMPO(4) (Carbon coated-LiMnPO(4), Carbon coated-LiMn(0.8) Fe(0.2)PO(4), and Carbon coated-LiFePO(4)), LiCoO(2) and LiNi(0.8)Co(0.15)Al(0.05)O(2) (NCA) composite electrodes with LiPF(6) solutions in ethylene carbonate (EC)/dimethyl carbonate (DMC) and EC/propylene carbonate (PC), was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis, coupled with mass spectrometry. The thermal reactions products were measured by XRD and electron microscopy. The LiFePO(4) and LiMnPO(4) cathode materials were found to have comparable thermal stability in their pristine and fully delithiated states. The onset temperatures of the thermal reactions are lower in EC/DMC than in EC/PC solutions but the specific heat evolution of all the thermal reactions are higher with EC-PC solutions. No evidence was found that delithiated LiMnPO(4) or Li[MnFe]PO(4) have lower thermal stability than delithiated LiFePO(4). The thermal reactivity of the layered LiCoO(2) and LiNi(0.8)Co(0.15)Al(0.05)O(2) cathode materials was found to be comparable to that of the LiMPO(4) materials. Oxygen release was detected from the layered compounds upon their heating around 200 degrees C. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3622849] All rights reserved.