Evaluating Degradation Mechanisms in Next-generation Electrode Chemistries

Abstract

Electrode degradation is one of the major obstacles hindering the implementation of new electrode chemistries into practical batteries. In this thesis, studies regarding the electrode degradation of some next-generation electrode materials have been explored, based on impedance and coulometry analysis. The impedance growth at Si-alloy and graphite blended electrodes were examined using symmetric cells. An inhomogeneous transmission line of active particles was developed to model this binary system. Both theoretical and experimental results show a small portion of low interfacial impedance particles can suppress the electrode interfacial impedance in blended electrodes. The next project is focused on the understanding of anode capacity fade in symmetric cells. A Li inventory model was proposed to interpret this fade in symmetric cells. A feasible approach to measure the solid-electrolyte-interphase growth, which results from the electrolyte reduction, was proposed. In the last project, an advanced galvanostatic cycling technology, termed current-corrected galvanostatic cycling, was proposed, in which each cycle’s current is adjusted to maintain a constant cycle duration based on the measured capacity of previous cycles. This method enables the measurement of true electrode/cell performance because unnecessary polarization is avoided.