The hybrid pulse power characteristics (HPPC) of Li(Ni0.8Co0.15Al0.05)O2 and Li1.1(Ni1/3Co1/3Mn1/3)0.9O2 electrode materials have been evaluated according to the FreedomCAR test manual and found to meet the power requirements for HEV applications. In addition to its excellent power capability, Li1.1(Ni1/3Co1/3Mn1/3)0.9O2 electrode material has shown much better safety characteristics than the Li(Ni0.8Co0.15Al0.05)O2 electrode material. To investigate the reason for this finding, Li(Ni0.8Co0.15Al0.05)O2 and Li1.1(Ni1/3Co1/3Mn1/3)0.9O2 powders were chemically delithiated using NO2BF4 oxidizer in an acetonitrile medium. The thermal gravimetric results show that both Li0.45(Ni0.8Co0.15Al0.05)O2 and Li0.55(Ni1/3Co1/3Mn1/3)O2 obtained powders release oxygen starting from 190 and 250°C with an overall oxygen loss of 11 and 6wt% at 600°C, respectively. The reactivity of the delithiated powders with several electrolytes was studied by differential scanning calorimetry (DSC) and accelerated rate calorimetry (ARC) techniques. The relationship between the safety characteristics of Li0.45(Ni0.8Co0.15Al0.05)O2 and Li0.55(Ni1/3Co1/3Mn1/3)O2 powders and their thermal stability was discussed in light of their structural rearrangement during thermal heating.