The overcharge behaviour of AlPO 4 -coated LiCoO 2 cathodes as a function of coating thickness is investigated in Li-ion cells at 1 and 2C overcharging rates. The AlPO 4 coating thickness is controlled by the concentration of the coating solution. During 1C-overcharging to l2V, the 5V plateau region, which is indicative of both electrolyte oxidation and an exothermic reaction between the electrolyte and the cathode, decreases with increasing AlPO 4 coating thickness (AlPO 4 concentration). Therefore, a Li-ion cell containing a P100-coated LiCoO 2 cathode (AlPO 4 coating thickness estimated as 1000A) does not show the 5V plateau, and displays the lowest cell external temperature of 60 o C, even at 12V. This suggests that the reaction at the 5V plateau strongly influences the final external temperature of the cell. When a higher current is applied (2C), cells with bare or P10-coated LiCoO 2 cathodes either burst or explode, and reach external temperatures of over 275 o C. By contrast, cells with P30 and P100-coated cathodes show only a swollen external appearance with temperature profiles similar to those at the 1C-overcharging rate.