Experimental study of capacity fading mechanism in multiple overdischarge on LiNi0.5Co0.2Mn0.3O2&LiMn2O4/graphite lithium-ion batteries

Batteries can be overdischarged in practical applications, which does not pose safety risks. However, overdischarge can have a significant impact on battery performance. In this work, LiNi0.5Co0.2Mn0.3O2 (NCM)&LiMn2O4 (LMO)/graphite batteries are used as the main body. The failure mechanism of the batteries under different temperatures (-10 °C, 25 °C, 45 °C) and different depth of discharge (DOD) (105% DOD and 110% DOD) is studied systematically through the electrochemical methods, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that the deep overdischarge and high temperature accelerate the degradation of electrolyte, separator and collector, and cause rupture and recombination of solid electrolyte interphase (SEI) film. These result in the loss of conductivity, active substances and lithium ions, in which the loss of lithium ions plays a dominant role. Moreover, the attenuation of positive active material mainly comes from NCM. Our research results are of great significance for researchers to understand the failure mechanism of lithium batteries under different conditions and can provide important guidance for the safe design of lithium-ion batteries.