In this work we evaluate the safety characteristics of an advanced Sn–C/EC:PC 1:1, LiPF6 PVdF gel electrolyte (GPE)/LiNi0.5Mn1.5O4 lithium ion polymer battery. The tests are performed by using a complex analysis that combines Differential Scanning Calorimetry (DSC) Thermal Gravimetric Analysis (TGA), and Mass Spectrometry (MS). This is a very convenient tool since it detects eventual thermal decomposition processes and provides information on the nature of their products. The results of the DSC–TGA–MS analysis are here reported and discussed. They demonstrate that both the anode and the cathode sides of the battery may stand temperatures up to ca. 200°C without undergoing thermal decomposition. This is a convincing evidence that the Sn–C/LiNi0.5Mn1.5O4 lithium ion polymer battery is safe.