Experimental analysis of overcharged Li-polymer batteries

Since safety hazards can occur during the life of a Li-ion battery, understanding its behavior under abusive conditions is important for the development of a safe cell. In this work, overcharge tests on commercial Li-polymer cells were conducted in a climatic chamber, resulting in gas evolution. A comprehensive post-mortem analysis of the abused cells was carried out: the exhaust gases were identified by gas phase chromatography coupled with a thermal conductivity detector (micro-GC/TCD), then flammable and toxic species were detected; the cathode and anode materials were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS), while the electrolyte composition was studied by Fourier-transform infrared spectroscopy (FT-IR). Interestingly, the ambient temperature seemed to affect the degradation of the cell materials and hence the composition of the evolved gas.