The performance of Cell-Batt® Li-ion cells and Sony 18650 cells using non-stoichiometric spinel and LiCoO2, respectively, as positive electrode material has been studied under several modes of charging. During cycling, the cells were opened at intermittent cycles and extensive material and electrochemical characterization was done on the active material at both electrodes. Capacity fade of spinel-based Li-ion cells was attributed to structural degradation at the cathode and loss of active material at both electrodes due to electrolyte oxidation. For the Sony cells both primary (Li+) and secondary active material (LiCoO2)/C) are lost during cycling.