This paper shows the research work based on experimental tests for identifying the most efficient extinguishing agent against LIBs fire. Experimental tests were conducted in cooperation with the National Fire Corps of Rome. For these experimental test LIBs typically used in electric, Hybrid or plug-in Hybrid vehicle have been chosen. The tested cell was placed on a metal grate inserted between two electric plates. The heat generated from the two plates induced the cell to thermal runaway and then to fire. In Total 11 Kokam SPLB pouch cells of 40 Ah and 3.7 V each have been used. Four different extinguishing agents have been tested: Water, F500, Foam and AVD. The results of each experimental tests were analysed in terms of chemical and physical action. An optimization model was developed for identifying the most efficient agent between all those tested. The results obtained from the experimental tests are preliminary results of the research concerning the extinguishing agents for fire of LIBs. The operating conditions chosen for these tests can be defined as ideal: the cell was not hidden by any obstacle (battery module or vehicle compartments).