The thickness of an AlPO4 coating significantly affects the thermal stability of a LiCOO2 cathode. Increasing the coating thickness leads to not only a decrease in the exothermic reaction between the cathode and the electrolyte but also to an improvement in the cycling performance. A 1 C rate overcharge experiment up to 12 V is a good example of the thermal stability of the cathode in the Li-ion cell. Further-more, increasing the AIPO(4) Coating thickness results in the lowest cell surface temperature, which is indicative of the degree of heat generation.