A detailed investigation of the effect of the thermal stabilizing additive, propane sultone (PS), on the reactions of the electrolyte with the surface of the electrodes in lithium-ion cells has been conducted. Cells were constructed with meso-carbon micro-bead (MCMB) anode, LiNi0.8Co0.2O2 cathode and 1.0M LiPF6 in 1:1:1 EC/DEC/DMC electrolyte with and without PS. After formation cycling, cells were stored at 75°C for 15 days. Cells containing 2% PS had better capacity retention than cells without added PS after storage at 75°C. The surfaces of the electrodes from cycled cells were analyzed via a combination of TGA, XPS and SEM. The addition of 2% PS results in the initial formation of S containing species on the anode consistent with the selective reduction of PS. However, modifications of the cathode surface in cells with added PS appear to be the source of capacity resilience after storage at 75°C.