Lithium-ion batteries have been introduced into large stationary energy storage systems. In recent years, used automotive batteries are being repurposed for use in stationary energy storage systems. It is of significant importance to understand the hazards associated with used cells and batteries and also determine the changes that occur to the cell components such as cathode, anode, separator and electrolyte. Under this study, cells were cycled to various levels of capacity loss and subjected to safety tests such as external short and overcharge. The cell cycling protocol included cycling the cells to the full end of charge and end of discharge voltages as well as reduced end of charge and end of discharge voltages. Cells were removed at 10%, 15% and 20% capacity loss and subjected to external short and overcharge tests. Cells were also cycled under hybrid electric vehicle usage profiles and at different temperatures to characterize the changes.