Cycling Aging in Different State of Charge Windows in Lithium-Ion Batteries with Silicon-Dominant Anodes

Abstract

Reducing the capacity utilization of the silicon-containing anodes and choosing the optimal full-cell voltage window improves the lifetime significantly. In this study, we investigate how different voltage windows affect the aging modes with a common 50% cycling depth. First, the cyclic stability, the polarization increase, and the anode potentials are analyzed for the different voltage windows using 70 wt% microscale silicon anodes and NCA cathodes with a lithium metal reference electrode to investigate the electrode-specific characteristics. Further, the anode thickness increase for different anode lithiation is quantified using a dilatometer setup. Finally, the underlying aging modes are quantified in the post-mortem analysis. In contrast to the literature, the highest voltage window is most beneficial for the lifetime since high anode delithiation potentials and high surface increases are avoided. The anode potential at the end of discharge, the charge-averaged full-cell potentials, and the resistance increase are a function of the state-of-health (SOH). The common underlying main aging mechanism is the loss of lithium inventory, followed by the loss of anode active material. In contrast, the loss of cathode active materials only plays a minor role.