Effect of Over-Discharge Depths on Battery Performance Over Long-Term Degradation

As the inconsistency of the battery module deteriorates, some cells are highly susceptible to over-discharge. In this study, the effects of depth of over-discharge (DoOD) on the performances over long-term degradation of L1 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{Ni}_{0.5}\mathrm{c}_{00.2}\text{Mn}0.3)\mathrm{O}_{2}$</tex> batteries are investigated. Based on the characteristic points of cut-off voltage, minimum voltage, maximum temperature, and maximum temperature rise rate, a method of dividing the full over-discharge process is proposed which can provide guidance for battery management systems (BMS) to enable early warning of over-discharge. There are anode graphite off and copper precipitation phenomenon by observing the internal structure of the over-discharge battery. When entering the severe over-discharge stage, the battery capacity decreases dramatically and crashes. The slight over-discharge stage is less damaging to the battery in the early stage, but as the number of over-discharge (NoOD) increases, the rate of capacity decay accelerates significantly. The DoOD has a more severe impact on battery performance than the NoOD. Compared to severe over-discharge, slight over-discharge causes less damage, but the NoOD accumulates this damage.