Investigation of the impact of different electrode inhomogeneities on the voltage response of Li-ion batteries

As commercial batteries and battery packs become larger and larger, one topic that is gaining interest is that of cell-to-cell variations and inhomogeneities. In this theoretical study, we use a degradation mode model along with a segmented cell approach to investigate the impact of different inhomogeneity modes on the performance of two typical Li-ion batteries. This unique approach shows that out of the nine considered modes (state of charge, rate, resistance, and capacity for each electrode as well as their offset), when at a mild level and randomly distributed, only three could affect performance, with two unlikely to happen in real cells because they would disappear during rest. Model results show that some of these inhomogeneities open the possibility of a snowball effect to induce local rate variations and lithiation inhomogeneities. Our study also shows that it is necessary to assess the level at which the paralleling occurs, electrode or full cell, as the model predicts an impact on how the current, and how much of it, is flowing within or in between the electrodes.