Calendar and cycle aging study of a commercial LiMn2O4 cell under consideration of influences by cell progress

Abstract

Abstract Aging characteristics of lithium-ion cells are investigated on the basis of commercially available LiMn2O4 cells. The effects of time, cell state of charge (SOC), and temperature are examined for the case of calendar aging. Likewise, charge throughput, depth of discharge (DOD), average SOC, charge rate, and realistic discharge profiles are analyzed for cycle aging based on a thorough aging test campaign. Aging properties are described by means of capacity, resistance, and differential voltage analysis (DVA). In addition to the square root-like capacity decrease over time and charge throughput, a significantly lower capacity loss is observed for low SOC scenarios. The influence of continuous cell chemistry improvement and a change of the cell chemistry from LMO to LMO-NMC is investigated over a period of 3 years. Initial characterization tests show a decrease in resistance and increase in capacity over the years. DVA and incremental capacity analysis (ICA) help to reconstruct the cell development progress by observing the rise of the NMC-induced ICA peak at about 3.5 V. A comparison of the three cell batches which were purchased over a period of three years indicates that, although the ICA changes, the capacity and resistance characteristics vary only slightly.